Chemistry Ii

 General CHEMISTRY II

Laboratory Manual

Dr. April French Dr. Allison Soult Dr. M. Meral Savas Dr. François Botha Dr. Carolyn Brock Mr. Charles Griffith Ms. Darla Hood Dr. Robert Kiser Dr. Penny O’Connor Dr. William Plucknett Dr. Donald Sands Dr. Diane Vance Dr. William Wagner

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FrenchA 6530-4 W14 Table of Contents

Introduction to the Laboratory...... v

Chapter 1 Laboratory Safety...... 1

Chapter 2 Laboratory Notebooks and Reports...... 11

Chapter 3 Techniques for General Chemistry Lab...... 25

Chapter 4 Using MeasureNet and Probes...... 33

Experiment 10 Scientific Writing and Integrity...... 43

Experiment 11 Molecular Structures...... 49

Experiment 12 Freezing Point Depression...... 59

Experiment 13 The Decomposition of Hydrogen Peroxide...... 63

Experiment 14

Chemical Equilibrium: Finding a Constant, Kc...... 69

Experiment 15 Standardization and Titration...... 73

Experiment 16 Chemistry Is pHun!...... 77

Experiment 17 Solubility of Calcium Hydroxide...... 83

Experiment 18 Analysis and Identification of Household Chemicals by Qualitative Analysis...... 87

Appendices A Laboratory Equipment...... 93 B Units and Constants...... 95 C Ions...... 99 D Solubility...... 101 E Standard Deviation...... 103

iii   General Chemistry II

 iv Introduction to the Laboratory

Tell me and I forget. Teach me and I remember. Involve me and I learn.

—Benjamin Franklin

In the first semester of lab, you learned a variety of lab techniques, as well as how to use basic glassware and equipment. As we continue in the lab, we will work more on developing your lab skills. However, there will be a much greater emphasis on applying what you have learned in lab by having students write the procedures needed to match the purpose of the experiment. This course will also review and reinforce the concepts you are learning or have learned in CHE 107. A laboratory course is different than a lecture course because it allows you to be involved in what is happening. I hope that you take full advantage of the opportunities available in this class to witness chemical principles in action, rather than seeing photos of, hearing someone talk about, or reading about them.

This laboratory manual contains information about all the experiments we’ll be doing as well as reference information about safety, lab reports, conversion factors, data on various elements and compounds, and more. Additional information is also available on the Blackboard website for this course (see the syllabus for information on accessing the course website). You are strongly encouraged to read all the information in the lab manual as well as the information posted on the website. Reviewing this information is critical to your success in the course. One of the most important thing you can do in this course is READ.

You cannot escape the responsibility of tomorrow by evading it today.

—Abraham Lincoln

v   General Chemistry II

There are many components to your grade for this Electronic Resources course, which are outlined in the course syllabus. You are There is additional information on experiments through responsible for reading the syllabus and adhering to all Blackboard including tutorials, videos (i.e., Using a assignment due dates and policies. You should read the Burette, Dispensing Liquids and Solids), and sample syllabus carefully and direct any questions you have to calculations. Some of the information will be required your Teaching Assistant and/or to the Lab Supervisor. It viewing, while other resources are there to help you is in your best interest to read the syllabus and get any when you need it. questions answered sooner, rather than later, so that you are not penalized for missing a due date or for misunder- There are many people involved in this course who each standing a course policy (i.e., mandatory attendance). have their own important role.

It is important that you take an active role in your learn- Lab Supervisor: The job of the lab supervisor is to su- ing by seeking help, asking questions, and participating pervise the teaching assistants, write quizzes and exams, in this course. Think about taking a class like a trip to help students, resolve student–TA problems, assign final the grocery store. You don’t go to the grocery and expect course grades, and other administrative tasks. The lab someone to know exactly what you need and bring it to supervisor has regularly scheduled office hours, but is you. You have to figure out what you need and go looking generally available at other times. for it. Maybe it’s a store you’ve never been in before and you have to walk around a little to find where the cereal Storekeeper: A member of the chemistry stockroom aisle is or the frozen foods are. As you walk through the staff works with the General Chemistry laboratory store, you may be offered help by clerks, but you’re sure courses by preparing chemical and unknown solutions, you can do it alone. Then when the clerks disappear, you setting up necessary supplies and reagents, and helping realize you do need help! Maybe you’ve found the cereal students replace missing and/or broken equipment. aisle, but you can’t find the Super Sugar Rings that you absolutely must have in order to function. Now, you’re Teaching Assistant: TAs are responsible for the direct faced with some choices: supervision of students in the laboratory, presentation of material in the lecture, helping students, grading lab 1. Keep looking in the same place you’ve been looking reports, and giving input on students’ course grades. because you’re positive you can do this on your own, after all if you’re able to get to the grocery store, then Student: Your job is to come to class prepared to do you should be able to find the Super Sugar Rings. the assigned experiment in the allotted time, work with other students on experiments, follow safety rules, keep 2. Give up because if you can’t find them, they must lab spaces clean, submit all assignments on time, and to not be there and you’ll have to do without. READ. You should read the syllabus, the lab manual, the website, and any other material that is given to you 3. Go find someone who can help you and ask them so that you know exactly what to expect in this course. where the Super Sugar Rings are and find out that because the Super Sugar Rings are on sale this week, The Director of General Chemistry oversees the admin- they are on the end cap of the soda aisle instead of istration of this course and can discuss problems or con- being in the cereal aisle. cerns that a student does not feel is resolved by discussing it with their TA and/or the Lab Supervisor. The same thing applies in this course, there are people to help you along the way but you have to find them and bring your questions to them so they know exactly what you need and can help you.

 vi  Chapter 1 Laboratory Safety

By its nature the chemical laboratory can be a dangerous place to work. The improper use of chemicals and equipment can cause severe and/or permanent damage to your body. And you are not the only one at risk. Your actions can affect your coworkers, those who follow, and the environment. One of the more important aspects of your chemistry lab experience will be learning how to perform experiments as safely as is humanly possible. You will learn how to protect yourself and others from the hazardous conditions created by your experimentation.

1-1 Safe Laboratory Practices It is common knowledge that doing chemistry is a hazardous activity. But so is driving a car or cooking. As with these other activities, the trick to safely working in a chemistry lab is to learn safe practices and develop safe working habits. This course is designed to teach safe lab practices and to help you develop habits that will lead to efficient, effective, and safe experimentation.

When performed correctly, the experiments presented in this course are safe. But this is a teaching lab. Mistakes will be made. Misinterpretation of the instructions or use of the wrong chemicals can result in a serious accident. And no matter how careful you are, the student working next to you may be doing something to endanger your health that you are helpless to prevent. No matter how much faith you have in your ability to work safely in the laboratory it is foolish to believe that an accident can’t happen to you.

The safety rules for working in this lab are designed with this idea in mind. If you faithfully adhere to these rules, and to your instructor’s precautions, you will find working in the chemical laboratory to be no more dangerous than working in a kitchen or driving a car.

1   Chapter 1 • Laboratory Safety

Keep in mind that safety rules don’t exist just to protect Chapter you and your lab mates. They are also intended to help instill safe working habits. Because habits are developed by repetition, it is expected that you will adhere to these rules at all times, regardless of the level of danger posed 1 by any particular experiment.

1-2 Safety Issues Eye Protection Your eyes are quite possibly the most fragile parts of your body. They are certainly very important and impossible to replace. And they face many dangers in a chemical lab. Proper protection of the eyes is mandatory in a chemical lab.

While explosions pose the most dramatic danger to your eyes, they are not very common in chemistry labs. The greatest danger is from splashed chemicals and fumes. Safety glasses provide protection against explosions, Figure C1.2. Eyewash fountain. but are not effective against splashes and fumes. Goggles with perforations are better, but still not adequate to There is no consensus on the danger related to wearing handle most chemical fumes. Only vented goggles or contact lenses in the lab. To date, there is no data that full safety shields are considered adequate to protect you shows either greater or lesser risk from wearing contacts. from splashed chemicals, flying glass, and noxious fumes. On the one hand, fumes that get in the eye will probably get under the lens. In this event the lens will aggravate any exposure. On the other hand, the contact lens will protect the cornea from direct chemical or physical contact.

Clothing You should think about what you will wear to lab. Many fabrics, such as nylon and polyester, react with common lab chemicals and burn well. Cotton clothing is the best. Figure C1.1. Vented goggles. To protect yourself against splashed or spilled chemicals you should also cover as much of your skin as is practical. Chemistry labs are equipped with eyewash stations That means a long sleeve shirt and long pants. Finally, as to provide first aid in the event some foreign body or a first line of defense, alab coat or apron can’t be beat. chemical enters the eye. You need to know the location and proper operation of the nearest eyewash to your work Don’t forget to consider what shoes to wear. Because space. Should you get a chemical in your eye, or should broken glass and spilled chemicals are common to the chemical vapors cause your eyes to water, immediately lab, closed-toed, non-absorbent shoes are a must. Con- wash your eyes with lots of water. To be effective, eye sider what would happen if you were wearing canvas washing must be continuous for at least 15 minutes. sneakers and socks and spilled an acid on your shoe. It would soak through the shoe and through the sock to your foot. In the time it would take you to get the shoe and sock off significant damage would be done.

 2 Chapter 1 • Laboratory Safety 

Chapter 1

Figure C1.3. Lab coat and apron. Figure C1.4. A lab safety station.

Chemistry labs are equipped with safety showers to Gloves provide first aid should you spill any chemical on your Hands present a special case. When we manipulate glass- skin or clothing. You need to know the location and ware and other laboratory equipment, we depend on our proper operation of the safety showers in your lab. Im- sense of touch to direct our activities. Gloves limit our mediately wash the affected area with lots of water and sense of touch and, therefore, our dexterity. Using gloves continue the washing for 15 minutes. increases the chance of an accident. In addition, the skin on hands is tougher than other skin. It comes with its A note on chemical contact. own protective layer of callouses. The decision to use Chemical burns can be just as nasty as heat burns gloves must balance the added protection they provide and often cause no pain until after damage is done. for the hands against the loss in dexterity. Any chemical contact with skin should be treated as a potential chemical burn. When this happens, contact There are two dangers your instructor. from chemical contact with skin: 1. destruction of tissue (chemical burns) and 2. poisoning due to absorption through the skin. When you will be working with a sufficiently dangerous chemical, you will be instructed to wear gloves.

3   Chapter 1 • Laboratory Safety

Reagents Labels Chapter The place where reagents are stored is known as the Check the label carefully before you use a reagent. Use of reagent bench. It will have most of the non-danger- the wrong reagent will ruin your experiment and could ous chemicals and other supplies that you will need to result in a serious accident. You also need to make sure perform your experiments. More dangerous chemicals you label everything you make and use in the lab. Many 1 are stored in a hood. The proper procedure for obtain- accidents result from assumptions made about unlabeled ing a reagent is to take an appropriate container to the containers. bench and take only what you need. Transporting a large container of any chemical can be hazardous and Precautions is to be avoided. Prior to each experiment your instructor will tell you how to properly use chemicals and equipment. You are expected to follow these instructions.

Waste Disposal You will need to become familiar with the various kinds of waste generated in a chemistry lab and the proper protocol for disposing of each. The kinds of waste are:

• Solid chemical waste. • Glass waste. • Garbage (stuff that can go in the garbage can: no glass, no chemicals). • Liquid organic waste.

Figure C1.5. A reagent bench. • Acidic water solutions. • Basic water solutions. When using reagent bottles you must be observant for • Heavy metal water solutions. spills. One common cause of chemical burns in a teaching lab is reagent on the outside of the bottle. It is easy • Drain water. (Only neutral water solutions that do to slop reagent down the outside of the bottle. If you do not contain heavy metals or organics can be poured so, make sure you clean it up. And watch for wet bottles! down the drain. No solids!)

When using reagent bottles you must also avoid contamination. You must develop habits that will minimize the possibility of contamination.

• NEVER set the cap to the reagent bottle down. Hold it between the second and third fingers of one hand. • NEVER insert objects (including pipets) into reagent bottles. Instead, transfer some of the reagent to a clean beaker and pipet from this container. • NEVER return unused reagent to the reagent bottle. Dispose of all unused reagent as chemical waste.

Figure C1.6. Chemical waste hood.

 4 Chapter 1 • Laboratory Safety 

Clean Up 1-3 Safety Assignment At the end of the class you are expected to turn off all 1. When are safety goggles to be worn in the lab? Who Chapter water and gas jets, return all borrowed items, and put must wear them? all of your equipment back into your locker and lock it. You also must leave a clean work bench for the student 2. What function do the hoods serve? When must you that follows. use them? 1

Accidents 3. Why must shoes be worn in the lab? Why are sandals Should an accident occur, it is important to notify prohibited? the instructor immediately. Even something as seemingly innocuous as cutting yourself on a broken 4. Your neighbor is carrying a bottle of concentrated piece of glass could become very nasty if that glass were nitric acid back to the lab bench. He trips and drops contaminated with a dangerous chemical. Let your in- the bottle which breaks and splatters its contents structor help to judge the severity of any incident. all over your legs. What do you do? What did your neighbor do wrong? Evaluation The most basic objective of a chemistry lab course is to 5. Make a diagram of your lab room. On this diagram teach you how to safely work in a chemical lab. Your indicate the location of the following items: grade will depend, in part, on how well you demonstrate your knowledge of safe laboratory practices. You should a. your workspace expect to see the material presented here on the exams you take. In addition, your instructor’s evaluation of your b. the hoods lab performance will be based, in part, on your adherence to safe laboratory practices and the lab rules. Finally, c. the nearest safety shower should you demonstrate a lack of regard for safety rules, or laboratory safety in general, you will be prohibited d. the nearest eyewash station from working in the lab. e. the nearest fire extinguisher

f. the first-aid box

g. the exits

h. the reagent bench

5   Chapter 1 • Laboratory Safety

Chapter 1

 6 Chapter 1 • Laboratory Safety 

Safety in a Chemistry Laboratory 4. Never work alone in the laboratory. Students must One of the most important aspects of any chemistry lab be supervised by a TA or the Lab Supervisor during Chapter is safety and this course is no exception. All students all experiments. are required to read the safety information in the lab manual, watch a safety video, sign and submit a copy of 5. Never leave an experiment or running equipment this form, and pass a safety quiz in order to participate unattended. Surprises are usually not a good thing 1 in this course. While some of this may seem repetitious, in a chemistry lab. it illustrates the importance we place on your safety and the safety of those around you. Violation of any safety 6. Only do the assigned experiment. Additional experi- rules will not be tolerated. Failure to remedy an unsafe ments are not allowed to ensure the safety of you situation will result in students being asked to leave the and those around you. laboratory. Missing an experiment due to a student’s failure to follow safety rules will not be considered an 7. Do not remove chemicals, equipment, or glassware excused absence. Students should read and understand from the laboratory. Any student alleged to have the rules listed below. removed any of the items listed above from the laboratory will be reported to the police. Any student 1. Your eyes are the most vulnerable part of your body caught removing any of the items listed above will to the dangers of working in a chemistry lab. You are be prosecuted. If a student is convicted, the case required to wear protective eyewear whenever you will be turned over to the Dean of Students and the or anyone else in the lab is transporting or using Department of Chemistry may recommend that the chemicals and/or glassware. Only chemical splash Dean of Students seek the harshest of University goggles which meet the current safety standards are sanctions, which includes expulsion. permitted. The cost of goggles is included in the cost of Chem21. When you have paid for Chem21 and 8. Do not wear gloves out of the laboratory, regardless submitted your access code online, you will receive of whether you have started working in the lab or your goggles from your TA during Experiment 10. not. You will be required to bring and wear your goggles to participate in lab. Sunglasses and prescription 9. Know the location of all safety equipment in the glasses are not acceptable forms of eye protection. room as well as the location of the nearest exit from Other types of goggles must be approved by the the room and building. Laboratory Supervisor. 10. If there is an accident, no matter how minor, contact 2. Appropriate clothing must be worn, including long your TA immediately. pants or skirts, shoes with closed toes (shoes which cover your feet completely are preferable), and shirts 11. Double-check all labels before using them in an which meet the top of your pants or skirt (i.e., no experiment to make sure it is the correct chemical bare stomachs or backs). Students not wearing ap- and concentration. Substituting another chemical or propriate clothing will be asked to leave the lab concentration could cause unexpected and danger- immediately. ous consequences.

3. No smoking, drinking, or eating (including gum) 12. Discard broken, cracked, or chipped glassware imme- at any time in the laboratory. All bottles, cups, and diately in the appropriate containers. Do not place food must be left outside the lab or placed into your glassware in the trash cans under any circumstances. closed backpack, bag, or pocket. Food or beverage Broken items can be replaced by contacting the containers must be disposed of prior to entering the stockroom. lab and cannot go into the trash cans in the lab.

7   Chapter 1 • Laboratory Safety

13. Tilt test tubes while heating, being careful not to 16. Dispose of waste in the appropriate container(s). Chapter point them at anyone. When in doubt, ASK!

14. Wipe down your workspace with a wet towel before 17. If the fire alarm goes off, turn off your equipment, leaving the laboratory to ensure that other stu- collect your belongings, and proceed to the nearest 1 dents are not unknowingly placed in contact with exit. All labs are to meet their TA on the hill where chemicals. the TA will take attendance. The Lab Supervisor will make all decisions regarding the completion of the 15. If you have any medical condition (allergies, preg- lab on a case-by-case basis. nancy, etc.) which may affect your performance in the lab, please notify the Lab Supervisor immediately so that any safety issues can be addressed.

By signing below, I indicate that I have read and understand the safety information provided to me in the lab manual, on the safety video, and by my TA. I also realize that it is my responsibility to follow all safety rules and that I will be removed from the laboratory for repeated violations of these rules.

Initial by each of the following statements to indicate that you have read them.

• I understand the policies of this course as outlined in the syllabus.

• I have seen the list of due dates for all assignments in the syllabus.

Name (print) ______

Signature ______

Date Section TA

 8 Chapter 1 • Laboratory Safety 

One of the most important aspects of any chemistry lab 4. Never work alone in the laboratory. Students must is safety and this course is no exception. All students be supervised by a TA or the Lab Supervisor during Chapter are required to read the safety information in the lab all experiments. manual, watch a safety video, sign and submit a copy of this form, and pass a safety quiz in order to participate 5. Never leave an experiment or running equipment in this course. While some of this may seem repetitious, unattended. Surprises are usually not a good thing 1 it illustrates the importance we place on your safety and in a chemistry lab. the safety of those around you. Violation of any safety rules will not be tolerated. Failure to remedy an unsafe 6. Only do the assigned experiment. Additional experi- situation will result in students being asked to leave the ments are not allowed to ensure the safety of you laboratory. Missing an experiment due to a student’s and those around you. failure to follow safety rules will not be considered an excused absence. Students should read and understand 7. Do not remove chemicals, equipment, or glassware the rules listed below. from the laboratory. Any student alleged to have removed any of the items listed above from the 1. Your eyes are the most vulnerable part of your body laboratory will be reported to the police. Any student to the dangers of working in a chemistry lab. You are caught removing any of the items listed above will required to wear protective eyewear whenever you be prosecuted. If a student is convicted, the case or anyone else in the lab is transporting or using will be turned over to the Dean of Students and the chemicals and/or glassware. Only chemical splash Department of Chemistry may recommend that the goggles which meet the current safety standards are Dean of Students seek the harshest of University permitted. The cost of goggles is included in the cost sanctions, which includes expulsion. of Chem21. When you have paid for Chem21 and submitted your access code online, you will receive 8. Do not wear gloves out of the laboratory, regardless your goggles from your TA during Experiment 10. of whether you have started working in the lab or You will be required to bring and wear your goggles not. to participate in lab. Sunglasses and prescription glasses are not acceptable forms of eye protection. 9. Know the location of all safety equipment in the Other types of goggles must be approved by the room as well as the location of the nearest exit from Laboratory Supervisor. the room and building.

2. Appropriate clothing must be worn, including long 10. If there is an accident, no matter how minor, contact pants or skirts, shoes with closed toes (shoes which your TA immediately. cover your feet completely are preferable), and shirts which meet the top of your pants or skirt (i.e., no 11. Double-check all labels before using them in an bare stomachs or backs). Students not wearing ap- experiment to make sure it is the correct chemical propriate clothing will be asked to leave the lab and concentration. Substituting another chemical or immediately. concentration could cause unexpected and dangerous consequences. 3. No smoking, drinking, or eating (including gum) at any time in the laboratory. All bottles, cups, and 12. Discard broken, cracked, or chipped glassware imme- food must be left outside the lab or placed into your diately in the appropriate containers. Do not place closed backpack, bag, or pocket. Food or beverage glassware in the trash cans under any circumstances. containers must be disposed of prior to entering the Broken items can be replaced by contacting the lab and cannot go into the trash cans in the lab. stockroom.

9   Chapter 1 • Laboratory Safety

13. Tilt test tubes while heating, being careful not to 16. Dispose of waste in the appropriate container(s). Chapter point them at anyone. When in doubt, ASK!

Initial by each of the following statements to indicate that you have read them.

• I understand the policies of this course as outlined in the syllabus.

• I have seen the list of due dates for all assignments in the syllabus.

Name (print) ______

Signature ______

Date Section TA

 10  Chapter 2 Laboratory Notebooks and Reports

During an experiment, students collect data and make observations about an experiment. This information should be recorded in your lab notebook and then used to complete the assignment(s) in the schedule. The lab notebook is used as an original record of your data, while a lab report is the formal presentation and discussion of the experiment and your results. The lab report should be typed and contain no errors, but the lab notebook will be handwritten and may contain errors.

Laboratory Notebooks Why are lab notebooks so important? A lab notebook is the original record of your data and should contain any information that you might need when writing your lab report. If there is something you are not sure you will need, write it down anyway. If you have it and don’t need it, it’s not a problem. If you need it and don’t have it, you have a problem.

If you plan a career that involves research, a lab notebook is very important. U.S. patents are decided by the date of invention, not the date of application. Failing to accurately document and date your findings means that the patent application could be denied which could result in the loss of substantial amounts of fame and fortune for you and/or your employer. If you are planning a career in a medical field, it is imperative that you accurately record all patient information. Failure to document symptoms and test results could result in a misdiagnosis which could lead to being sued for medical malpractice.

11   Chapter 2 • Laboratory Notebooks and Reports

Before Lab

Chapter 2

 12 Chapter 2 • Laboratory Notebooks and Reports 

After Lab

Chapter 2

13   Chapter 2 • Laboratory Notebooks and Reports

The lab notebook (purchased separately) should be used • It is okay if the lab notebook is not perfect or to record the following information: contains errors. • Do not record data in the middle of the pro- • Basic information cedure. Chapter • Name • Never remove pages from your lab notebook. The • Experiment number and name pages are numbered sequentially and should remain • Date (all pages should be used in sequential intact even if you use additional pages for calcula- 2 order) tions or other notes. • Name of lab partner • Mark out any errors with a single line so that the original information is still legible but the line clearly • Course and section number indicates that it is incorrect. • Signature of student • Organize data in tables when collecting multiple • Signature of TA values. • Procedure planned and carried out in lab. Do not • Label all values (i.e., volume of water used). print out the lab manual for lab. • Do not have “orphaned” numbers. All values • List of any changes to the procedure published in should have labels and units. the lab manual. • Include units for all numbers. • This should include changes announced in • Record all qualitative observations. class, on Blackboard, etc. • Record all unknown numbers/letters. • Qualitative data (i.e., after addition of HCl, a lemon yellow precipitate formed) • Record concentrations of all solutions used. • Quantitative data (i.e., mass of the metal cube— At the end of each lab session, have your TA sign your 2.5434 g, 2.3425 g, 2.4344 g) lab notebook and then turn in the copy of your results to them. This allows your TA to verify data presented in • Note the description of the item as well as the your report and identify any recurring problems in the units. experiment. The data in your report should match that • File names of any data collected and saved elec- in your lab notebook exactly. Any discrepancies should tronically. be explained prior to submitting the report. • Include some type of identifying information 1 for all electronic data files such as the initial Assignments or final temperature, approximate equivalence Part of your grade in this course will be based upon the point, etc. assignments submitted for each experiment. There are three main types of assignments which you will complete • All calculations, making sure to show all steps. If you in this course: make an error, you, a TA, or Lab Supervisor can use this information to find the error. • Chem21: Online data analysis which will be com- When writing information in your lab notebook, you pleted for each experiment. should always do the following: • Lab Report: Students will complete either a section or a full report for most experiments. See the course • Always write in blue or black ink. schedule for a description of what is due. All final • Always write your data directly in your lab notebook. versions of reports or portions of them are to be • Do not write the information on a separate piece submitted electronically on Blackboard. of paper and transfer it.

1 Some information and descriptions of categories for the grade sheet come from http://labwrite.ncsu.edu, a project funded by the National Science Foundation and available to students everywhere.  14 Chapter 2 • Laboratory Notebooks and Reports 

• Peer Review: Your TA and two of your classmates will Lab reports are submitted electronically and copies of use a feedback form to help you improve your lab re- all reports for both the current and previous semesters port before you submit the final copy on Blackboard. are kept on file. Reports submitted electronically are compared to all reports submitted in both previous and • Worksheet: A longer assignment on Chem21 labs, current semesters. If you copy from another student Chapter generally completed on weeks you don’t submit a lab or the lab manual, you will get caught. Using report, is worth more points than normal Chem21 someone else’s work without giving them the appropri- assignments. ate credit is plagiarism, which is an academic offense. See the syllabus for an explanation of how each assign- Academic offenses are taken very seriously by the De- 2 ment contributes to your final course grade. partment of Chemistry and the University of Kentucky.

Laboratory Reports1 Penalties for academic offenses can be as severe as sus- The purpose of a lab report is to explain the theory pension, dismissal, or expulsion from the University. behind the experiment, present the results, and discuss The minimum penalty in general chemistry lab courses how the results relate to the theory. Someone who has is a zero on the assignment and a reduction of the final not done the experiment or even read the experiment course grade by one letter grade. If you have questions in the lab manual should be able to read your lab report about academic offenses or plagiarism, please contact and understand what you were trying to do, see the your TA or the lab supervisor; review the relevant rules summary of your data, and understand the results of of the University Senate (Rule 6.3); or contact the Writ- your experiment. Lab reports allow you the opportu- ing Center. nity to interpret your data and relate it (or not) to the theory behind the experiment. While it is much easier to Each part of the lab report will be discussed in more explain data that agrees with the theory, you will prob- detail, but the following are some general tips on writ- ably find that in one or more experiments, you might ing lab reports: get an unexpected result. Do not change your data or use someone else’s data just because your numbers • Reports must be completely typed. “look bad.” What is more important is that you either see potential sources of error that could have led to the • Save early, save often. results and/or that you try to explain the results that • Computers lock up and break down. Save your disagree with the underlying theory. work and back up your files. • Microsoft Word is preferred when writing your We understand that some students have never written reports. a lab report before or have written reports following a different format. If you are in this situation, you are not • As the lab manual went to press, Microsoft alone. All students should follow the guidelines presented Office is available free to students athttp:// here to write their reports and contact their TA for help, download.uky.edu. Help with the download if needed. and/or installation is available from the IT Cus- tomer Service Center in McVey Hall. Do NOT copy another student’s work or from • Microsoft Office is installed on all campus the lab manual when writing your lab report. computers. Do not use someone else’s report as a “guide” • Students should not use Microsoft Works as or a “template.” Students may discuss content it does not handle images well and frequently but lab reports (including text, tables, equa- creates files larger than 10 MB which will not tions, graphs, etc.) should be written indepen- be accepted on Blackboard. dently of other students, their lab reports and the lab manual. Do not resubmit any part of a • Mac users should see the FAQ for additional report you have turned in before. information.

15   Chapter 2 • Laboratory Notebooks and Reports

• Microsoft Word is also available in campus as an example. Each item is graded on a scale of 1 (ex- computer labs. cellent) to 0 (poor) in 0.25 point increments. This value is then multiplied by the point value to get your score • If Word is not an option to write your report, for that particular section of the report. Your TA should you may use OpenOffice www.openoffice.( Chapter include comments in the grade worksheet returned to org) but you must save the file as the type you and/or in a general e-mail to all students. If you “Microsoft Word 97/2000/XP.” have questions about the grade on your lab report, you • Reports must be submitted electronically using the should see your TA first since they are the ones that 2 link given in the course syllabus and on Blackboard. graded the report. If you still have questions, contact Paper or e-mailed copies will not be accepted. the Lab Supervisor. • Proofread your lab report before submitting it to check for grammatical or spelling errors. Contact your TA as soon as you have questions so that you can make the needed corrections on future lab re- • Do not wait until the last minute to complete your ports. It is in your best interest to talk to your TA about report. If you need help late at night or in the early your grades as questions arise. Waiting until all assign- hours of the morning before the report is due, you ments have been submitted is not helpful for you. may not be able to get it before the report is due.

• It is always a good idea to make sure you can The format for lab reports varies among different fields of open any data files shortly after your lab session science (i.e., physics, biology, chemistry) and there can in case there are any problems with the file. be differences within one field. While the components of • If you are unable to complete the paper, it is each may be generally the same, they may use different better to take a zero than face academic offense section titles, expect different things, or have different charges. standards. Likewise, any lab reports you wrote in high school may be very different than what you will do in • Your lab report will be graded by your TA who may this class. The following information discusses what to have their own formatting preferences (spacing, do and not do for each section of your lab report. Please font, graph size, etc.). note that the items listed follow the grading sheet which • Always separate parts of your lab reports with head- will be used to grade your report. ings for each section (i.e., Results, Discussion, etc.). • With the exception of the conclusion, the rest of the Title report should be written in third person. File named correctly and in the correct format • Follow the format experimentnumber_lastname_ • Instead of saying “I recorded the mass of the firstname.doc sample,” say “The mass of the sample was recorded.” • Jane Doe submitting the report for Experiment #8 would name the file 8_doe_jane.doc Lab reports will be graded electronically and an Excel spreadsheet will be returned to you via Blackboard with • The file must be in MS Word 2003 or later format. your grade. An example of the spreadsheet is included Header information on page 17. This also serves as an outline for explaining Above the title, you should give some basic information the different parts of a lab report. You should receive your including the following: grade within one week of the due date of the report. If you are not receiving your grades in a timely • Name manner, please contact the Lab Supervisor. • Course and section number • TA’s name The point value for each item will vary with each experiment depending on the level of difficulty for a particular • Lab partner’s name section. The values in the sample grade sheet are meant • Date

 16 Chapter 2 • Laboratory Notebooks and Reports 

Student Name: Jane Doe Experiment #: 7 Section Points 0, 0.25, 0.50, 0.75, 1.0 Poor to Excellent Miscellaneous Chapter Deductions for late reports, safety, etc. (use minus sign) or points for rough draft (#2 & #11 only) Title (3) File named correctly and in correct format 1 1.00 2 Header information 0.75 0.75 Describes lab content concisely, adequately, appropriately 1 1.00 Introduction (6) Successfully establishes the scientific concept of the lab 1 2.00 Effectively presents the objectives and purpose of the lab 0.75 1.50 Includes support or reasoning for objectives, including equations and formulas 1 2.00 Methods (1) Includes appropriate reference or enough details to replicate unpublished procedure 1 1.00 Discussion (14) Statement of purpose/hypothesis 1 2.00 Opens with summary of relevant results 0.75 2.25 Explains if results support original purpose/hypothesis 1 3.00 Explains why the results support the original purpose/hypothesis or not 0.75 2.25 Addresses other issues important to the lab and their effect on the results 0.5 1.50 Conclusion (2) Convincingly describes what has been learned in the lab 1 1.00 Has successfully learned what the lab is designed to teach 1 1.00 Presentation (4) Citations and references adhere to proper format 0.75 0.75 Formatting of report is correct 1 1.00 Report is written in scientific style: clear and to the point 0.5 0.50 Grammar and spelling are correct 0.75 0.75 Points Earned 23.25 Total Possible Points 30

TA: Joe Smith Date: 10/15/2009

7_Jane Doe

17   Chapter 2 • Laboratory Notebooks and Reports

Describes lab content concisely, adequately, Includes support or reasoning for objectives including all and appropriately needed chemical equations and formulas and mathemati- The title should give the reader an idea of what the report cal formulas is about. A good title should: • Explain how the experiment will support the pur- Chapter pose/hypothesis. • Be descriptive and concise. • Gives information specific to this experiment. • Be appropriate to the experiment. • Include any relevant chemical equations and/or • Not be too long (usually no more than one line) and 2 formulas. Use Equation Editor for any mathemati- not a complete sentence. cal formulas.2 • Not be identical to the lab manual. • Include any relevant mathematical formulas, defin- Introduction ing any variables, and an explanation of when the The purpose of the introduction is to give some back- formula can be used (i.e., discuss any limitations of ground and theoretical information for the experiment formula). in order to explain what concepts or theories are appli- Methods cable to the experiment, explain what you are trying to The methods section should outline the exact experimen- determine in the experiment, and why this experiment tal procedures followed. If the procedure is published in should support the theoretical concepts stated. the lab manual, you should not rewrite the procedure, but instead reference it and make note of any changes. Successfully establishes the scientific concept of the lab • Gives all relevant theoretical and background infor- When procedure is in lab manual mation for the experiment. • Include all necessary information for the source of • Explains the concepts in a logical manner. the procedure including page numbers and whether • Discusses general concepts of experiment. there are changes or not. • Using the lab manual or other sources as a reference • Changes, including changes in equipment or materi- is acceptable, but the use of direct quotations should als, are to be clearly explained. be minimal. • If there are no changes to the procedure in the lab Effectively presents the purpose/hypothesis and objectives manual, you should state “No changes to the pub- for the lab lished procedure.” • The purpose/hypothesis should be specific and per- • Do not rewrite or quote the complete procedure tinent to the experiment. from the lab manual. • The purpose/hypothesis should in some way predict • Do not include any results or data in the procedure. the outcome of the experiment based on theoreti- When procedure is not in lab manual cal information, not on the data collected for the • Write procedure clearly so that it can be replicated experiment. using only what is written. • Objectives should be stated in your own words. The • Include a list of needed chemicals, equipment, and/ objectives for the lab given in the report will not or materials. be the same as those given in the lab manual and should focus on the overall goal of the lab. • Include all steps that you planned to do and steps that were added when you actually did the experiment.

2 Equation Editor is available in MS Word and OpenOffice. For help in finding, installing and/or using Equation Editor on your computer, see the information posted on Blackboard or search for more information on the Web using a search engine, such as www. google.com.

 18 Chapter 2 • Laboratory Notebooks and Reports 

• As a rule of thumb, give enough detail so that your • Make sure all numerical values have the correct mom could repeat the experiment. units and are correctly formatted (i.e., for standard deviation: 36.1 ± 1.1 g). • Do not include how to calculate values or that you need to do a calculation. • Do not repeat all of the data reported in the results Chapter section. • Cite any source used when developing your procedure. Explains if results support original purpose/hypothesis of experiment Results • State whether or not experimental results support The results section of a report generally includes your 2 purpose/hypothesis. data as well as any calculations and/or graphs. Rather than writing a results section in your report, you will Explains why the results support or don’t support the original complete this online at www.chem21labs.com. You purpose/hypothesis will receive an e-mail with your login information after • Compare the experimental results to the theoretical the last day to add a class. You will need to purchase predictions. access either by buying an access code at the bookstore • Explain why the results support or don’t support the or directly through the website. Access is good for one purpose/hypothesis. semester. You will need this code when you log in to Chem21 to have access for the semester. Addresses other issues pertinent to the lab and their effect on the results • Discuss at least three potential sources of error. Discussion Potential sources of error are things that you know The discussion section is where we bring the theoretical happened and things that could have happened. For information (from the Introduction) and the experimen- each source of error, you should have three things: tal information (from the Results) together. The discussion is also where potential sources of error should be 1. Describe in detail the error that could have oc- discussed. The order of information in the discus- curred. sion is important. In general, the discussion should 2. Explain exactly how the error would have af- be longer than the introduction. If not, the introduction fected the results. Do not say “The results would is too long and/or the discussion is too short. be skewed.” Be specific and state if results would be lower or higher than expected. Statement of purpose/hypothesis 3. Explain how the error could have been pre- • One or two sentences restating the original purpose/ vented. hypothesis of the experiment based on the theoretical and background information. • Example: Loss of sample on the filter paper would have resulted in a lower mass of product. This would • Do not change your purpose/hypothesis because it have caused the mass percent of copper in the final does not match your results. formula to be lower than the theoretical value. • Place this at the very beginning of the discussion This could have been prevented by transferring the section. sample more carefully from the filter paper into the Summary of relevant results beaker. • Include this information immediately after your • Addressing sources of error requires a critical review restatement of purpose/hypothesis. of each step of the experiment rather than saying • Gives summary of key results including, but not “I messed up” or “we didn’t know what we were limited to, average values, percent error, and/or doing.” standard deviation.

19   Chapter 2 • Laboratory Notebooks and Reports

Conclusion Original Text from Advanced Inorganic Chemistry by The conclusion gives you the opportunity to discuss what F. Albert Cotton and Geoffrey Wilkinson you learned in this experiment. It can be written in first Crystalline hydrates of metal ions and of organic sub- person (i.e., “I learned…”). This is also an opportunity stances, especially those with N–H and O–H bonds, are Chapter for the TA to evaluate your understanding of the experi- numerous. For metal ions, the oxygen is always bound to ment and related concepts through your work in the lab, the metal and the lone pairs on it can be directed toward how you worked with your lab partner, and through an the metal and involved in bonding but can, however, 2 evaluation of your lab notebook. also form H bonds. Convincingly describes what has been learned in the lab Paraphrase and In-Text Citation • State what you have learned and how it relates to Many metal ions can form crystalline hydrates (Cotton other topics or to real-life situations. 96). • Give any reasonable suggestions for improving the experiment. Quotation and In-Text Citation For the crystalline hydrates of “metal ions, the oxygen • You should not describe your lab partner’s ability or is always bound to the metal” (Cotton 96). inability to function in a lab setting. Has successfully learned what the lab is designed to or teach • The TA will evaluate your understanding of the topic Cotton states that for the crystalline hydrates of “metal based on the overall quality of your report, your ions, the oxygen is always bound to the metal” (96). work in the lab, and the information entered into your lab notebook. Bibliography/Works Cited • Ask questions about concepts you don’t understand. Book with one or more authors Author(s). Title of Book. Place of Publication: Publisher, • Work with your lab partner to complete the experi- Year of Publication. ment.

• Include all data and observations in your lab note- Example book and do so following the guidelines given at the Cotton, F. Albert & Geoffrey Wilkinson. Advanced Inor- beginning of this chapter. ganic Chemistry. New York: John Wiley & Sons, 1988. Presentation Whenever you are submitting your work to someone Website else to read, you should pay attention to the general ap- Before you use a website as a reference, make sure you pearance and formatting. Remember that your TA will be evaluate the quality of the content. Just because it is reading your report on a computer screen so you want posted on the internet doesn’t mean it is true. to make sure it is legible and easy to read. Use of Wikipedia has its place, but is not appropriate When referencing other sources, including this for information that can be found in your textbook or lab manual, you should use the MLA style. Some this lab manual. simple examples are shown below, but if you have questions refer to a style guide. Additional help is Author(s). Name of Page. Date of Posting/Revision. Name available in the Writing Center (more information at of institution/organization affiliated with the site. Date http://www.uky.edu/AS/English/wc/). of access .

 20 Chapter 2 • Laboratory Notebooks and Reports 

For additional information on the MLA style, check out • Use third person in the report (first person is accept- the following resources: able only in the conclusion). • Proofread your report before submitting. It is usu- • https://owl.english.purdue.edu/owl/ ally best to let it sit for a day (or at least a few hours) Chapter resource/747/01/ and then reread the report. You might catch errors in grammar or spelling or realize that you omitted • http://bcs.bedfordstmartins.com/resdoc5e/ some important information. RES5e_ch04_o.html Grammar and Spelling 2 • Proofreading your report, perhaps out loud, will help Citations and References Are Formatted Correctly you detect grammatical errors. • In-text citations are included for any paraphrased or quoted material. Remember that direct quotations • A list of common grammatical errors can be must have quotation marks and a reference. found at http://bcs.bedfordstmartins. com/everydaywriter5e/default. • In-text citations should include author’s name and asp#798016__807752__ or search on an internet page number. search engine such as www.google.com for • References should have all the necessary informa- “common errors in grammar.” tion. • Since all reports are typed on a computer, use the • Include an alphabetized list of references at the end spell-check feature in your word processor. For words of your report. not in the standard dictionary, such as chemical • When referencing a website, follow the style above names, look them up in your lab manual, textbook, and include the month and year the page was ac- or use an internet search engine such as www. cessed. google.com to find the correct spelling. Formatting of Reports Is Correct • Make sure all sentences are complete sentences and • Use subscripts and superscripts in chemical and have subject–verb agreement. mathematical formulas. • If you need help with your writing skills, visit the • Use the correct type of arrows in all reactions. Writing Center on the 5th floor of the .W T. Young library. More information about the Writing Cen- • Use Equation Editor when typing mathematical ter can be found at http://www.uky.edu/AS/ formulas. English/wc/. You can go to the Writing Center • Follow any guidelines for margins, fonts, etc., as for help or use some of their online resources (look given by your TA (see page 23). under “Student Resources”). Report Is Written in Scientific Style • All statements and explanations are logical. • Make sure that relationships between theoretical concepts are clear. • Do not include unnecessary information (i.e., “This report isn’t very good because I was out of town this weekend” or “I couldn’t complete the calculations because I didn’t write down my data and my lab partner didn’t send it to me.”). • Do not repeat information unless it adds some value or insight to the concepts discussed in the report.

21   Chapter 2 • Laboratory Notebooks and Reports

Chapter 2

 22 Chapter 2 • Laboratory Notebooks and Reports 

Semester and Year ______

Room Number CP-

Information About My TA Chapter Name (first and last) ______

Contact Information ______(e-mail and/or phone) 2

Office Hours ______All office hours are held in CP-25, the General Chemistry Learning Center.

Other Information ______

Formatting Preferences for Lab Reports Ask your TA the following questions so that you know exactly what they want. Since they are the one grading your report, it is in your best interest to follow their formatting preferences. If they request something specific and you do not know how to do it, you can ask them or look in the help files of your word processing program.

1. Do you have a preference for single or double spacing?

2. Do you prefer a particular font? What about font size?

3. What size margins do you prefer?

4. Do you want a separate title page or can the title be at the top of the first page?

5. Should references be listed on a separate page or can they be placed at the end of the conclusion?

6. Do you have any preference for formatting tables, such as showing all gridlines?

7. Do you have any other preferences for the format of lab reports?

23   Chapter 2 • Laboratory Notebooks and Reports

Chapter 2

 24  Chapter 3 Techniques for General Chemistry Lab

One of the goals of this course is to teach students some basic laboratory techniques that they will use in this course as well as in future laboratory courses. Using correct techniques is important for several reasons. Proper technique:

1. reduces the error in experimental results.

2. prevents damage to equipment.

3. prevents contamination of reagents.

4. helps maintain a safe environment in the lab.

Dispensing Solids Reactions are performed using reagents in both the liquid and solid phase so it is important to know how to dispense solids from the stock reagent bottle. The following steps should be performed when dispensing solids from a reagent bottle:

1. Obtain a small beaker, watch glass, or weigh boat to transfer the solid reagent.

2. Determine the approximate amount of the solid needed.

3. Locate the stock reagent bottle.

4. Remove the lid and lay it top-down or hold the lid. Never lay lids facedown as this can lead to contamination of the stock reagent.

5. Pour the approximate amount of solid needed into your container. Rotate the bottle slowly to help pour the sample slowly without getting too much.

25   Chapter 3 • Techniques for General Chemistry Lab

6. Replace the lid on the reagent bottle and take your Some additional tips for dispensing liquid reagents. sample to your bench or the balance area. • Never return excess reagents to the stock bottle. Some additional tips for dispensing solid reagents: • Wipe up any spills to avoid any injuries when some- • Whenever dispensing solids, you should be careful one else comes to the stock reagent area. not to create a “dust cloud” of the chemical to avoid Chapter inhalation and eye exposure. • Never insert a dropper or any other object into the stock reagent bottles in order to prevent contamina- • Always leave stock reagent bottles in their original tion. 3 location so that everyone has access to them. Never take reagent bottles to the balance area or to your • Always leave stock reagent bottles in their original bench. location so that everyone has access to them.

• Never insert a spatula or any other object into the • Concentrated acids and bases should be used in the stock reagent bottle in order to prevent contamina- hood. Do not remove the bottles from the hoods. tion. • The brown dropper bottles used for concentrated Dispensing Liquids acids and bases should be tilted to dispense the Liquids tend to be easier than solids to obtain since they reagent. Do not remove the lid. are easier to pour and it is easier to estimate the volume of a liquid than the mass of a solid. The following steps Using an Analytical Balance should be performed when dispensing liquid from a The analytical balance is often used in many chemis- reagent bottle: try laboratories. It allows us to determine the mass of a substance. Although the terms mass and weight are 1. Obtain a small beaker or test tube to transfer the frequently used interchangeably, they are not the same liquid reagent. thing. Mass is the amount of something while weight is a measure of the pull of gravity on the object. Mass 2. Determine the approximate amount of reagent is independent of location, while weight is not. The needed. mass of an object on the moon will be identical to its mass on Earth. The weight of an object will change. For 3. Locate the stock reagent bottle. example, a 100-pound object on Earth will weigh 16.5 pounds on the moon and 234 pounds on Jupiter. 4. Remove the lid and lay it top-down or hold the lid. Never lay lids facedown as this can lead to contami- Most labs use electronic analytical balances but some still nation of the stock reagent. use what is known as a triple beam balance. The General Chemistry Labs use electronic analytical balances which 5. Pour the approximate amount needed into your look similar to that shown in Figure C3.1. To increase container. Measure the exact volume needed when the accuracy of your measurements, always use the same you return to your bench. If you take the time to balance throughout an experiment. measure exact volumes at the stock reagent area, you cause delays for other students. 1. Turn the balance on and check that all doors are closed or cover is on. 6. Replace the lid on the reagent bottle and take your sample to your bench. 2. Press the “0/Tare” button to set the balance to zero.

 26 Chapter 3 • Techniques for General Chemistry Lab 

• Use a weigh boat (see Figure C3.2) or a small beaker to hold the sample.

• Never pour reagents into a container in the balance. Always remove the container, add the reagent, and

©Hayden-McNeil, LLC then place in the balance.

Chapter • Record all digits given on the display so that you can keep as many significant figures as possible after your calculations. 3 • Always clean the balance after each use.

Display Balance pan Figure C3.1. Electronic analytical balance.

Tare means to adjust the zero point on a balance. ©Hayden-McNeil, LLC 3. Place the object on the balance pan and close the doors or replace the cover. Figure C3.2. Weigh boat.

4. Allow the value to stabilize and record all digits on Using a Graduated Cylinder the display in your lab notebook. One piece of glassware commonly used in lab is a graduated cylinder which is used to measure the volume of 5. Remove the sample from the balance. liquids needed. Graduated cylinders come in many sizes, from 10 mL (or smaller) to 4 L. The following steps should 6. Use the brush to remove any solids from the balance. be used when measuring the volume of a liquid using a graduated cylinder: 7. Close the doors or replace the cover and turn off the balance. 1. Obtain a clean, dry graduated cylinder.

Some additional tips for using an electronic analytical 2. Pour the amount needed into the cylinder. balance: 3. Record the exact volume used rather than trying to • Balances are fragile pieces of equipment. You should obtain the volume listed in the procedure. not move a balance except when necessary. Always open and close cover gently. a. Look for the bottom of the meniscus (see Figure C3.3). The meniscus will be much less promi- • Never take reagent bottles to the balance area. Get nent in plastic than in glass due to differences the approximate amount needed in a beaker or other in the adhesive interactions between the liquid container and take that to the balance area. and the container.

• Never return excess reagent to the stock bottle. If b. Position yourself so that your eyes are level with you have excess reagent, offer it to someone else or the meniscus. dispose of it correctly. Do not leave it in the reagent area or near the balances. c. Using the markings on the cylinder, determine the volume of the liquid in the cylinder.

27   Chapter 3 • Techniques for General Chemistry Lab

d. Always estimate one additional decimal place which indicates the temperature at which the cylin- beyond the markings of the cylinder when ders are calibrated. If used at a different temperature, reading the volume to improve the accuracy of there can be some error in the measured volume. your value. It is assumed that the last digit has been estimated. 100 4. Add the liquid to the reaction as directed in the Meniscus Chapter procedure.

5. Clean the cylinder to prevent contamination with 90 3 its next use. Some additional tips for using a graduated cylinder:

Eye level 80 • Always estimate one additional decimal point. Look- ing at the example shown in Figure C3.3, we can see that the volume is between 88 and 89. By estimating the next digit between these two markings, we Reading 88.6 mL 70 ©Hayden-McNeil, LLC increase the accuracy of our measurement. Since the last decimal place is assumed, someone seeing a volume of 88 mL would think it is between 80 and 90. If someone sees a volume of 88.6 mL, then this lets them know the volume is between 88 and Figure C3.3. Determining the volume in a graduated 89 which is a far more accurate description of the cylinder. volume of the liquid. Using a Buret Another piece of volumetric glassware is called a buret. • Volumes given in the procedure are approximate. It A buret is often used when the amount of liquid to be is more important to record the actual volume used added to the reaction is unknown. The liquid can be rather than spending time trying to get to the exact dispensed from the buret as needed and the volume is volume listed in the procedure. determined by recording the initial and final volume of the buret. To use a buret, do the following: • Use the smallest graduated cylinder that will contain your sample for increased accuracy. For example, 1. Obtain a clean, dry buret, a ring stand, and a buret clamp. • Use a 10 mL cylinder to measure 3 mL of solution. 2. Set up the buret as shown in Figure C3.4. • Use a 50 mL cylinder to measure 18 mL of solution. 3. Close the stopcock (handle should be perpendicular • Never return excess reagent to the stock bottle. If to the buret). Put a small beaker under the buret in you have excess reagent, offer it to someone else or case there are any leaks. dispose of it correctly. 4. Use a funnel and fill the buret with the necessary • Volumetric glassware usually has markings indicat- solution. ing if they are “TD” or “TC,” which stand for “to deliver” and “to contain.” A temperature is also listed 5. Remove the funnel from the buret.

 28 Chapter 3 • Techniques for General Chemistry Lab 

Initial volume 0.40 mL 0

1 Buret clamp

Chapter ©Hayden-McNeil, LLC

23 3 Final volume Buret 23.80 mL

24 Ring stand

25 Flask

Figure C3.5. Reading initial and final volumes on a buret

©Hayden-McNeil, LLC Figure C3.4. Setting up a buret. Some tips on using a buret:

• The volume markings go from top to bottom. 6. Open the stopcock (handle should be parallel to the buret) to allow 1–2 mL of liquid to drain from the buret. Repeat if there are still air bubbles present in • Always estimate one additional decimal point. the tip of the buret. By estimating the next digit between these two markings, we increase the accuracy of our measurement. 7. Record the initial volume (see Figure C3.5). The initial volume does not have to be at zero. It will • Remove the funnel and check for air bubbles before save you time and effort if you just record the initial recording the volume. volume as it is instead of trying to get the initial volume to zero. Estimate one decimal place beyond • If you need more volume than the buret contains, the markings on the buret. record two pairs of initial and final volume data and combine the differences from the two pairs. 8. Dispense the amount of liquid needed. Be careful not to dispense past the bottom markings on the • If you have a broken buret, please take it to your TA. buret. The tip and stopcock can be replaced and the barrel can be repaired, depending on the location of the 9. Record the final volume (see Figure C3.5), estimat- break. ing one decimal place beyond the markings on the buret. Subtract the initial volume to determine the volume dispensed.

29   Chapter 3 • Techniques for General Chemistry Lab

Gravity Filtration temperatures at which the vapors of the liquid can Separations play an important role in chemistry and ignite in air. Use caution when placing samples range from separating a solid from a liquid to separating rinsed with flammable solvents in the oven. two isomers of a compound. Gravity filtration is one of the simplest forms of separation and is used to separate a • Do not overfill the funnel when adding the sample liquid from a solid. Much like you drain cooked spaghetti to the funnel. Make sure the liquid does not go above in a colander, a solid can be separated from a liquid by the top edge of the filter paper. Chapter pouring the sample through a piece of filter paper in a funnel. Think of the filter paper as a colander with really, Vacuum Filtration really small holes in it. To perform a gravity filtration do While gravity filtration is effective, it can be slow and the following: vacuum filtrations are usually much more efficient than 3 gravity filtrations. A Büchner funnel is one type of fun- 1. Obtain a funnel, filter paper, and flask. If you want nel that can be used for a vacuum filtration. It is shaped to filter the liquid into a beaker, you would also need differently from a regular funnel and has many small a ring stand and an iron ring. holes instead of one large hole. Rather than waiting for the liquid to go through the filter paper on its own, a 2. Initial the filter paper with a pencil and find its mass. vacuum filtration pulls the liquid through. A vacuum can be created in a filtration flask when the filter flask 3. Fold the filter paper in quarters and then open into is connected to a water aspirator. As water flows down a cone (see Figure C3.6a). Place the cone into the through the faucet, air is pulled in through the side arm funnel which can be inserted into the neck of the and out of the connected flask. This creates a vacuum in flask or placed in a ring over a beaker (see Figure the flask which then pulls the liquid through the Büchner C3.6b). funnel and filter paper.

4. Wet the filter paper with the solvent of the solution 1. Obtain a Büchner funnel, filter flask, vacuum tubing, being filtered (commonly distilled water). filter paper, ring stand, clamp, and clamp holder.

5. Using a stirring rod to help, pour the liquid into the 2. Initial the filter paper with a pencil and find its mass. funnel. Then use a wash bottle to wash the remain- ing sample out of the beaker (see Figure C3.7). 3. Set up the funnel as shown in Figure C3.9 and place the piece of filter paper in the funnel. The filter paper 6. Rinse the solid a few times with an appropriate should lay flat in the funnel. solvent. 4. Connect the vacuum tubing to the side arm of the 7. Allow the filtration to continue for several minutes aspirator on the faucet (see Figure C3.8). after it appears complete. This allows any additional solution to filter through which will require less time 5. Turn the water on. for the solid to dry, if applicable. 6. Use a small amount of the solvent to wet the filter 8. Remove the filter paper from the funnel, place on a paper. pre-massed watch glass, and place in an oven to dry. 7. Using a stirring rod to guide the solution, pour the Some tips for doing a gravity filtration: sample to be filtered onto the filter paper. Pour small portions to avoid getting solid underneath the filter • If the solvent used is flammable, use caution when paper. heating a sample to dry. Liquids such as ethanol and acetone have low flash points which are the lowest

 30 Chapter 3 • Techniques for General Chemistry Lab 

Figure C3.6a. Folding filter paper for gravity filtratio

Tip of funnel touches the beaker wall

Figure C3.7. Performing a gravity filtration

31   Chapter 3 • Techniques for General Chemistry Lab

8. Allow the filtration to continue for several minutes Stirring rod after it appears complete. This allows any additional solution to filter through which will require less time for the solid to dry, if applicable.

9. Disconnect the tubing to break the vacuum before turning off the water. Chapter

10. Use a spatula to help remove the filter paper from Filter paper the funnel. Place the filter paper on a pre-massed 3 watch glass and place in oven to dry. Büchner funnel 11. Check the procedure for the experiment to determine whether the filtrate (liquid) should be pre- served for additional experiments or disposed of.

to aspirator on water faucet

Filtration flask

Figure C3.8. Aspirator connection. Figure C3.9. Vacuum filtration setup

Some tips when doing a vacuum filtration:

• If you notice a leak under the sink, disconnect the vacuum first and then turn off the water. Notify your TA.

• If the solvent used is flammable, use caution when heating a sample to dry. Liquids such as ethanol and acetone have low flash points which are the lowest temperatures at which the vapors of the liquid can ignite in air. Use caution when placing samples rinsed with flammable solvents in the oven.

 32  Chapter4 Using MeasureNet and Probes

Students will collect data in the lab using the MeasureNet workstation and a variety of probes. The workstation is the user interface which allows students to set up experiments, and then collect data which is then uploaded to the Chem21 server where it can later be retrieved to complete the data analysis for the experiment. The data is displayed on the workstation display as it is collected. The probes connect to the workstation via the ports on the bottom of the workstation. Figures C4.1 and C4.2 show a picture of a student workstation with the buttons divided into groups based on their function as well as the bottom of the workstation where the probes are connected.

Please be aware that components of electronic data collection systems are expensive and must be handled with care. Follow the directions carefully to both collect good data and to protect the equipment.

The TA in the lab will log students into the workstation and can monitor their data collection throughout the lab session. Once logged in, students can begin to collect data. Do not begin work until your TA has confirmed that you are logged in to the correct workstation. The instructions on the following pages provide a general outline for use of the MeasureNet workstation and probes. However, students are expected to adapt these instructions for the specific experimental needs as they write their procedures. Carefully read the information on the display as there is sufficient information there to help guide you to the next step.

33   Chapter 4 • Using MeasureNet and Probes

Chapter 4 Figure C4.1. Front view of MeasureNet workstation.

Figure C4.2. Bottom view of MeasureNet workstation.

Operation of the MeasureNet Workstation

1. Connect the appropriate probe to the workstation. 6. When indicated in the probe instructions, select “CALIBRATE” and follow the directions on the dis- 2. Press the power button on the workstation and see play. that the status is “online.” 7. Choose “SETUP” to specify limits of the axis (i.e., the 3. Press “MAIN MENU” to see a list of probes. probable range of your data) for display purposes. Values outside these limits will still be collected but 4. Use the function keys (F1, F2, etc.) to select the cor- will not appear on the workstation display. rect probe. a. After data collection is complete, you can 5. Use the function keys again to select the appropri- change the limits to replot the current data set. ate type of experiment (e.g., temperature vs. time, pressure and temperature, etc.).

 34 Chapter 4 • Using MeasureNet and Probes 

8. Use the arrows to highlight (look for asterisks on either side) the value that needs to be changed, type in the correct value, and press “ENTER.”

9. Select “DISPLAY” to accept all values.

10. Press “START/STOP” to start data collection. Data will continue until the x max value or until you press “START/STOP” again. pH Electrode and Calibration Chapter For this titration experiment, we will use a pH electrode to measure the change in pH as we add the standard solution to our analyte solution. In order to obtain accurate data, the pH electrode must be calibrated against Figure C4.3. Drop counter. 4 solutions of known pH. Because we will be measuring pH values over a wide range, we will calibrate the electrode Calibration against two solutions with pH values of 4.00 and 10.00. 1. Obtain a pH sensor, ring stand, drop counter, and It is only necessary to calibrate before the first titration any needed clamps. Complete the setup of the drop that you perform in lab that day. Changes in signal from counter and pH electrode as shown in Figures C4.3 the electrode do change over time but the change during and C4.4. one lab period is not significant. 2. Obtain approximately 20–25 mL of each of the buf- fers (pH 4.00 and pH 10.00) in separate plastic 50 mL The pH electrode is a delicate and expensive piece of beakers. These will be used to calibrate the pH probe equipment. Use caution to avoid breaking the tip and do and should not be used for any other purpose. not use it to stir a solution. The only moveable/remove- able part on the electrode is the storage bottle. 3. Remove the storage bottle from the pH electrode, connect it to the workstation, and insert it into the Drop Counter opening on the drop counter so that the cap rests When using the pH electrode, we will also be using a in the recess. device known as a drop counter. As each drop of liquid passes through the “counting slot” with its infrared 4. Rinse the pH electrode with distilled water and collect beam, it is counted. By entering both the initial and the waste into a 250 mL beaker. This will be used as final volumes on the buret, the average drop size can be your waste beaker throughout the experiment. determined, which, along with the number of drops, will allow us to graph a pH vs. volume curve. This titration 5. Use a thermometer to measure the temperature of curve can then be used to determine the equivalence the pH 4.00 buffer solution and record the value. point which is then used to determine the concentration 6. Place the pH 4.00 buffer solution underneath the pH of the analyte (unknown) solution. electrode and lower the electrode into the solution.

When using a drop counter, it is imperative that you set 7. Press “MAIN MENU” on the workstation and select the equipment up correctly and that the solution dis- “pH/mV” from the menu and then select “pH v pensed from the buret is done so in drops. If the buret is Volume.” opened to allow a constant flow of liquid, the data will be unusable. 8. Select “CALIBRATE” and the workstation will prompt you to enter the temperature and the correct pH of the solution (e.g., 4.00).

35   Chapter 4 • Using MeasureNet and Probes

9. Once the pH reading on the screen stabilizes, press “ENTER.” The value on the screen may not read 4.00; you are just waiting for the value to stop changing.

10. When prompted, enter the pH of the second buffer solution (e.g., 10.00). Remove the electrode from the first buffer solution andrinse well with distilled water into your waste beaker.

11. Place the beaker with the pH 10.00 buffer below the Chapter electrode and lower it into the solution.

12. Once the pH reading on the screen stabilizes, press “ENTER.” The value on the screen may not read 4 10.00; you are just waiting for the value to stop changing.

13. Press “DISPLAY” on the workstation. The pH value should be within  0.05 of the actual pH of the second buffer solution. If not, you need to redo the calibration.

14. Raise the pH electrode and remove the buffer solution. Rinse the electrode well with distilled water.

Titration 1. Obtain approximately 40–50 mL of your titrant Figure C4.4. Titration setup. (usually your solution of known concentration) in a 100 mL beaker. 6. Open the stopcock to drain enough titrant to fill the 2. Rinse the buret with 3–5 mL of the titrant by pour- tip (~1–2 mL). At this time, you also need to deter- ing it in the buret so that it covers all sides and then mine how far to open the buret so that the solution draining it into your waste beaker. Do three rinses. drips from the buret. The solution must drip in order to collect data. 3. Attach a buret clamp to the ring stand and insert the buret so that the tip of the buret is directly over the 7. Once you have found where to turn the stopcock so “counting slot” on the drop counter. The solution that the solution will dispense dropwise, close the from the buret must drop through the counting slot stopcock and remove the waste beaker. to collect data. 8. Obtain a sample of the analyte (usually the unknown 4. Place the waste beaker underneath the buret and solution). Remember that the larger volume used, close the stopcock. the longer it will take to titrate (<25 mL is usually a safe place to start). Using a graduated cylinder, deter- 5. With a funnel, fill the buret with the titrant solution. mine the exact volume. Don’t forget to estimate one Remove the funnel. decimal place beyond the markings on the glassware!

 36 Chapter 4 • Using MeasureNet and Probes 

9. If needed, add distilled water to the beaker so the 15. Allow the titrant solution to drip into the analyte total volume (distilled water plus analyte) will be solution until the titration is complete. When com- ~40–50 mL of solution in the 150 mL beaker and plete the pH value will plateau (~10–12 for a basic then add the known volume of the analyte solution. titrant and ~1–4 for an acidic titrant).

10. Place the 150 mL beaker underneath the drop coun- 16. When complete, simultaneously press “START/STOP” ter and lower the pH electrode into the solution. The on the workstation and close the stopcock on the pH electrode should be just above the bottom of the buret. beaker so that you can gently swirl the solution. 17. Record the final volume reading in your lab note- 11. Check that the buret tip is directly over the “count- book and enter it into the workstation. Chapter ing slot” so the drops will go through the opening and into the beaker. Do not open the stopcock yet. 18. Continue by saving the data (see directions on page 41). 12. Begin the titration by pressing “START/STOP.” The 4 workstation will prompt you to enter the initial 19. Refill buret as needed and repeat until experiment volume. Enter the actual volume reading from the is complete. At least three good titrations should be buret. Remember to record the volume to the second collected for each set of needed titrations. This may decimal place when you estimate one decimal place mean that you need to collect at least four titrations beyond the markings on the buret. The buret does so that the outlier can be excluded. not have to start at zero. 20. Dispose of waste in the appropriate location and 13. Carefully, turn the stopcock on the buret so that the clean all equipment and glassware before returning titrant drips into the analyte solution. You may need it to the correct location. to make small adjustments to the stopcock so that 21. Rinse the pH electrode with distilled water, remove it the solution continues to drip at approximately 1 from the drop counter, and replace the storage bottle. drop per second. The red LED light will flash each The electrode needs to be stored wet in the storage time it detects a drop. solution, not in distilled water and never stored dry. 14. Gently swirl the beaker while the titrant is being See your TA if you need additional storage solution. added, being careful to keep the beaker under the 22. Carefully wipe any liquid from the surfaces of the buret at all times. drop counter.

Reminders for Use • Always rinse the probe with distilled water after each use.

• Store only in the pH storage solution. Never store dry or in water.

• Calibrate at the start of the lab session.

• Solutions must drop through the drop counter. A flow of solution will cause errors in your data.

Figure C4.5. Typical titration curve.

37   Chapter 4 • Using MeasureNet and Probes

Pressure Probe 3. Use the function keys to select “PRESSURE & TIME.” The pressure probe can be used to measure the pressure of the contents in a container. It measures “gauge pres- 4. Press “CALIBRATE” and follow the instructions on sure,” which is the difference in pressure between the the screen. atmospheric pressure and the pressure of whatever is 5. Press “DISPLAY.” connected to the probe. Like an open-ended manom- eter, you need to add the reading from the gauge and Measuring Pressure vs. Time the atmospheric pressure to get the actual pressure. The 1. Attach the tubing to the connector in the stopper. atmospheric pressure can be found on the barometer located in the lab. 2. Prepare, but do not mix, any solutions needed. Chapter 3. Mix the solutions and quickly insert the stopper into the container. 4 4. Allow data to collect until experiment is complete. 5. If you do not see an increase in pressure, repeat the trial and check your system carefully for leaks.

6. Continue by saving the data (see directions on page 41).

7. Repeat as needed for additional trials.

Reminders for Use • Do not over-tighten the fittings. Stop when you feel resistance. Figure C4.6. Pressure probe. • Do not attempt to remove tubing from sensor. Calibration • Hot plates are hot; plastic melts. Use caution when 1. Connect the pressure sensor to the workstation using probes and hot plates at the same time. without anything attached to the sensor.

2. Press “MAIN MENU” on the workstation. Press the appropriate function key to select “PRESSURE.”

Figure C4.7. Pressure probe connections. A. Direct connection of the syringe; B. Four-way stopcock connection; C. Luer-to-hose barb fitting

 38 Chapter 4 • Using MeasureNet and Probes 

Temperature Probe 7. Once the experimental setup is complete, press The temperature probe can be used in the range of –50°C “START/STOP” on the workstation to begin collect- to 125°C and can be used in a variety of substances. ing data. While calibration is necessary to determine an accurate temperature relative to an external accepted value, many 8. Once data collection is complete, press “START/ experiments are more focused on the change in tem- STOP.” perature. In these cases, the absolute temperature is not 9. Rinse the temperature probe with distilled water and important as long as the probe behaves uniformly (i.e., dry. Return to the correct storage location. offset by 1°C throughout the range of measurements). 10. Continue by saving the data (see directions on page Chapter 41).

Reminders for Use • Hot plates are hot; plastic melts. Use caution when 4 using probes and hot plates at the same time.

Colorimeter A colorimeter can be used to measure the amount of light of a particular wavelength. Unlike scanning instruments which scan a range of the electromagnetic spectrum (e.g., infrared, visible, X-ray, etc.), a colorimeter monitors a single wavelength. Light of the appropriate wavelength is absorbed by the solution. As the concentration of the absorbing species increases, the amount of light absorbed Figure C4.8. Temperature probe. will increase. Sometimes the value is reported as the percent transmittance which is inversely proportional Measuring Temperature to the absorbance. 1. Connect the clamp to the ring stand to hold the temperature probe.

2. Connect the temperature probe to the MeasureNet workstation.

3. After verifying that your TA has logged you in to the workstation, press “MAIN MENU” on the workstation.

4. Select “TEMPERATURE.”

5. Select “TEMP v TIME.” Figure C4.9. Colorimeter. 6. Select “SETUP” to check limits which are determined by the range of experimental values you expect. Data The colorimeters used in the lab are known as dual-beam outside this range will still be collected but will not colorimeters because there are two beams of light that appear on the display. If necessary, press the arrow will go through two paths inside the colorimeter. One keys to select which variable to edit (marked by as- of the beams will go through a cuvette containing the terisks on either side of value), key in the new value solvent or other appropriate solution (cell holder “R”) to and press “ENTER.” account for any light absorbance by the cuvette and/or

39   Chapter 4 • Using MeasureNet and Probes

the solution/solvent. This will be known as the blank or a. Always record the exact volumes used since it is reference solution. The other beam will go through the unlikely that you will get the exact amounts. For sample (cell holder “S”) being studied so the reported example, instead of 1.00 mL, you might have value will actually be a reporting of the difference in the 1.08 mL. It is very important that you record the amount absorbed between the two samples, which gives exact volume so that your concentrations will us a direct relationship between the concentration of the be correct in the graph which will be used to light-absorbing species and the amount of light absorbed. determine the concentration of the unknown. The use of a dual beam also eliminates variations in the signal due to changes in the intensity of the light. 8. Prepare solutions as needed for the experiment.

Chapter 9. Rinse both of the cuvettes twice with the blank R detector solution. Rinsing involves pouring a small amount light beam source splitter ratio display of a solution in a cuvette and pouring it out. This 4 S detector removes any residual liquids from the cuvette to make sure the concentration of the solution is not affected by those residual liquids. Dispose of the Figure C4.10. Dual-beam schematic. rinsings in the appropriate manner.

The color of a substance is determined by its interaction 10. Fill the cuvettes with the blank solution and cap the with light. We can see blue because a sample absorbs all cuvette. Use a lint-free tissue to wipe the sides of the colors of light except blue, which is reflected. Alterna- cuvette being careful to hold the cuvette by the top tively, we can see blue because its complementary color to avoid fingerprints on the sides. (the color across from it on the color wheel) is absent from the light. 11. Place one of the cuvettes with the blank solution in the cell holder marked “R.” Use care when inserting Measuring Absorbance the cell in the holder as it is designed to hold the 1. Connect the colorimeter to the workstation. Make cuvette by the corners only (see Figure C4.11). sure no other probes are connected to the workstation. Cuvette position 2. After verifying that your TA has logged you in to the Cuvette holder workstation, press “MAIN MENU” on the workstation.

©Hayden-McNeil, LLC 3. Select “COLORIMETRY/FLUOR/TURB” and then Figure C4.11. Cuvette holder in colorimeter. select “COLORIMETRY.”

4. Use the function key to select the appropriate wave- 12. Place the second cuvette with the blank solution in length. the cell holder marked “S.”

5. Select “KINETICS” on the workstation. 13. Slide the colorimeter lid closed and press “ENTER.” The minimum and maximum percent transmittance 6. Obtain the necessary reagents. will be adjusted at this time and will take approximately 10 seconds to complete. 7. Prepare your blank or reference solution which should contain everything except the light-absorb- 14. After this is complete, select “DISPLAY.” ing species.

 40 Chapter 4 • Using MeasureNet and Probes 

15. Leave the blank solution in the cell holder marked Reminders for Use “R” and remove the blank solution from the cell • Use care when placing cuvettes into the colorimeter holder marked “S.” to avoid scratching the cuvette and to avoid spilling solution into the colorimeter. While colorimeters 16. Rinse the second cuvette with your first solution. are built to be durable, spilled liquids inside any electronic equipment can destroy it. 17. Fill the cuvette with your first solution and cap the cuvette. Use a lint-free tissue to wipe the sides of the • Record exact volumes used. cuvette being careful to hold the cuvette by the top to avoid fingerprints on the sides. • Always clean cuvettes with a lint-free tissue and handle carefully. Natural oils on your skin which Chapter 18. Place the sample cuvette into the cell holder marked are transferred to the cuvette will interfere with “S.” Use care when inserting the cell in the holder. your results. 19. Wait until the value has stabilized and then, in your Saving Data 4 lab notebook, record the absorbance for the solution. 1. After data collection is complete, press “FILE OP- TIONS” and choose “SAVE.” 20. Pour the solution into a waste beaker. 2. Enter the appropriate three digit code (see experi- 21. Repeat steps with sample solutions until the absor- ment information for details about what code to bance for all have been measured. Leave the refer- use). The code is important as it allows the data to ence cuvette in the colorimeter for the duration of be correctly imported into Chem21. the experiment. 3. Press “ENTER.” 22. Pour the solutions from both cuvettes into a waste beaker. 4. Check with your TA to make sure the file was saved and uploaded correctly. Check with your TA to see if you will enter data now or on Chem21. 5. Press “MAIN MENU” to start another trial, if needed.

23. Push the “MAIN MENU” key and then select “OTH- Reminders ER.” • Data is saved automatically to Chem21.

24. Select “MANUAL ENTRY.” • When you log in to Chem21, your MeasureNet data will be available. Other data (e.g., mass of substance) 25. Key in the value of the exact concentration for your will be entered manually into Chem21. first solution and press “ENTER.” You will need to calculate this before entering your values. • Data can also be downloaded from Chem21 for viewing and processing in an external program. 26. Key in the value of the absorbance for your first solution and press “ENTER.”

27. Repeat for each of the solutions. Double-check all values before saving data. If you need to change the data, use the arrow keys to select a data point and then key in the new value and press “ENTER.”

28. Continue by saving the data (see directions that follow).

41   Chapter 4 • Using MeasureNet and Probes

Chapter 4

 42