DOCSLIB.ORG

Intermediate Answer Key Chapter 21: Acids & Bases

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Intermediate Answer Key Chapter 21: Acids & Bases CK-12 Chemistry Concepts - Intermediate Answer Key Chapter 21: Acids & Bases 21.1 Properties of Acids Practice Questions Watch the video at the link below and answer the following questions: http://www.youtube.com/watch?v=uahCEZf831c 1. Which of the four solutions are acids? 2. Stop the video at 0:30 minutes and predict conductivities. 3. What color did the acids turn when universal indicator was added? Answers 1. HCl and CH3COOH (acetic acid). 2. The acids and NaCl are ionized and will conduct electricity. 3. Red. Review Questions 1. Are all acids electrolytes in water? 2. What color does blue litmus turn in the presence of an acid? 3. What does the reaction of an acid and a base produce? Answers 1. Yes. 2. Red. 3. Water and a salt. 21.2 Properties of Bases Practice Questions 1 Read the material at the site below and answer the following questions: https://sites.google.com/site/sodiumhydroxsite/Acidsandbasesbasics/chemical- properties-of-bases 1. What does the reaction between an acid and a base produce? 2. What is this reaction called? 3. What does the reaction of a base with an ammonium salt form? Answers 1. A salt and water. 2. Neutralization. 3. A metal salt, ammonia, and water. Review Questions 1. Are bases electrolytes? 2. What color does a base turn phenolphthalein? 3. Do bases react with metals the same way that acids do? Answers 1. Yes, some are strong electrolytes and some are weak. 2. Red. 3. No. 21.3 Arrhenius Acids Practice Read the material at the link below and answer the following questions: http://dwb4.unl.edu/Chem/CHEM869R/CHEM869RLinks/www.nidlink.com/7Ejfromm/arr henius.htm 1. What was Arrhenius’ first scientific idea? 2. What did his Ph.D committee think about it? 3. What did he win for this idea? 4. Write the generic equation for dissociation of an Arrhenius acid. Answers 1. Electrolytes dissociated in solution. 2. They did not like it and gave him a D for his research. 2 3. The 1903 Nobel Prize in Chemistry. 4. HA → H+ + A-. Review Questions 1. What is an Arrhenius acid? 2. What is a hydronium ion? 3. Is H2SO4 a monoprotic or a polyprotic acid? Answers 1. Yields a hydrogen ion upon dissociation in water. + 2. H3O . 3. Polyprotic. 21.4 Arrhenius Bases Practice Questions Read the material at the link below and then take the quiz: http://flatworldknowledge.lardbucket.org/books/introductory- chemistry/section_16_01.html Answers Answers are at the web site. Review Questions 1. What is an Arrhenius base? 2. What is one reaction that will form an Arrhenius base? 3. Are alkaline earth bases very water-soluble? Answers 1. One that forma a hydroxide ion in water solution. 2. Alkali metal + water → base + hydrogen gas. 3. No, they only partially ionize. 3 21.5 Bronsted-Lowry Acids and Bases Practice Questions Read the material at the link below and answer the following questions: http://www.chemteam.info/AcidBase/Bronsted-Lowry-AcidBase.html 1. Why is water considered a base in the reaction between water and HCl? + 2. Why is H3O considered an acid? 3. Why is the chloride anion considered a base? Answers 1. Because it can accept a proton from the HCl to form the hydronium ion. 2. Because it can donate a proton. 3. Because it can accept a proton to form HCl. Review Questions 1. What is a Brønsted-Lowry acid? 2. What is a Brønsted-Lowry base? 3. How does ammonia function as a Brønsted-Lowry base? Answers 1. A molecule or ion that donates a proton. 2. A molecule or ion that accepts a proton. 3. The lone pair electrons on the N atom can accept a proton. 21.6 Bronsted-Lowry Acid-Base Reactions Practice Questions Read the material at the link below and do the problems at the end of the selection: http://s-owl.cengage.com/ebooks/vining_owlbook_prototype/ebook/ch16/Sect16-1- b.html 4 Answers Answers are on the web site. Review Questions 1. In the reaction between ammonia and water, how does the ammonia serve as a base on the left-hand side of the equation? 2. How does the ammonium ion serve as an acid on the right-hand side of the equation? 3. Write the conjugate acid-base pairs for the reaction between two water molecules illustrated above. Answers 1. It accepts a proton. 2. It donates a proton. + - 3. H2O/H3O and OH /H2O. 21.7 Lewis Acids and Bases Practice Questions Do the practice problems associated with Section 3 Lewis Theory at the link below: http://staarhelper.com/Mr_B_Science/daily_lessons/cacid.htm Answers Answers are given on the web site. Review Questions 1. What is the difference between a Lewis acid or base and a Brønsted Lowry acid or base? 2. What is required to happen in Lewis acid-base reactions? 3. Do all Lewis acid-base reactions involve protons? Answers 5 1. The Lewis system looks at electron pairs while the Brønsted-Lowry approach focuses on proton exchange. 2. A covalent bond must be formed. 3. No. 21.8 Ion-Product of Water Practice Questions Read the material on the first two pages of the link below and do those practice problems: http://www.vigoschools.org/~mmc3/Chem%201/Lecture%20Notes/L2%20- %20Hydrogen%20Ions%20and%20pH%20-%2015.1.pdf Answers 9. a. basic, b. basic c. acidic d. neutral. 10. 1 x 10-11M, basic Review Questions 1. What is an acidic solution? 2. What is a basic solution? 3. What is the [OH-] of a solution which has a [H+] of 1 x 10-5M? Answers 1. Concentration of hydrogen ions is greater than the concentration of hydroxide ions. 2. Concentration of hydroxide ions is greater than the concentration of hydrogen ions. 3. [OH-] = 1 x 10-9M. 21.9 The pH Scale Practice Questions 6 Read the material at the link below and answer the following questions: http://staff.jccc.net/pdecell/chemistry/phscale.html 1. What is a buffer? 2. How much more acidic is vinegar than grapefruit? 3. How much more basic is soapy water than milk of magnesia? Answers 1. A solution that resists pH changes when acid or base or added. 2. Ten times more acidic. 3. One hundred times more basic. Review Questions 1. What is one value of using pH instead of molar concentrations? 2. Is coffee an acidic or a basic substance? 3. If a material has a pH of 9.3, is it acidic or basic? Answers 1. A simple number can be used instead of an exponential expression. 2. Acidic. 3. Basic. 21.10 Calculating pH of Acids and Bases Practice Questions Carry out the requested calculations at the link below: http://www.sciencegeek.net/APchemistry/APtaters/pHcalculations.htm Answers Answers are given at the web site. Review Questions 1. What is the pH of a 4.5 x 10-3 M HI solution? 7 2. What is the pH of a 3.67 x 10-5 M NaBr solution? 3. If we have a weak base with a low ionization constant, can we assume that the [OH-] in the solution is equal to the concentration of the base? Answers 1. pH = 2.4. 2. pH = 9.56. 3. No, the hydroxide ion concentration will not be equal to the molar concentration of the base because all the OH- will not be in the dissociated form. 21.11 The pOH Concept Practice Questions Do all calculations at the link below that involve pOH: http://www.sciencegeek.net/APchemistry/APtaters/pHcalculations.htm Answers Answers are provided on the web site. Review Questions 1. What is the formula for calculating pOH? 2. What pOH value is indicative of an acidic solution? 3. A pOH value of 3 would indicate what type of solution? Answers 1. pOH = -log[OH-] 2. A value of less than 7. 3. A basic solution. 21.12 Strong and Weak Acids and Acid Ionization Constant (Ka) Practice Questions 8 Read the material at the link below and answer the following questions: http://www.chemguide.co.uk/physical/acidbaseeqia/acids.html 1. Why is the [H2O] factor not included in the expression for Ka? 2. When we write H+, what are we really talking about? 3. Which is the weaker acid: methanoic or ethanoic acid? Answers 1. Because the concentration of the water is virtually constant. 2. Hydroxonium ions. 3. Ethanoic acid. Review Questions 1. Why is the chloride ion the weakest conjugate base? 2. What is the percent ionization in a 0.1 M solution of acetic acid? 3. Which is the stronger acid: HF or benzoic acid? Answers 1. It is incapable of accepting H+ ions. 2. 1.3%. 3. Hydrofluoric acid. 21.13 Strong and Weak Bases and Base Ionization Constant (Kb) Practice Questions Read the material at the link below and answer the following questions: http://www.chemguide.co.uk/physical/acidbaseeqia/bases.html 1. In the presence of hydroxide ions, which way does the equilibrium shift for the equation showing the dissociation of water? 2. What percentage of ammonia in solution actually produces hydroxide ions? 3. How does the position of equilibrium relate to the strength of a weak base? Answers 1. The equilibrium shifts toward the left side of the equation, according to the Le Chatelier’s Principle. 9 2. 1%. 3. The further the equilibrium is to the left, the weaker the base. Review Questions 1. Define a strong base. 2. Define a weak base. 3. Which is the stronger base: pyridine or urea? Answers 1.
Load more

Recommended publications
  • 1 Experiment 6 Determination of the Equilibrium Constant For
    Experiment 6 Determination of the Equilibrium Constant for Bromocresol Green Reading assignment: Chang, Chemistry 10th edition, Chapter 15: Acids and Bases, sections 1-5. Goals To determine the acid dissociation constant (Ka) for bromocresol green (BCG), an acid-base indicator. Discussion Acid-base indicators are often used to demonstrate the end-point of an acid-base reaction. Examples include phenolphthalein and the mixture of indicators used in universal indicator solution. Acid-base indicators are + – weak acids that dissociate into a hydronium ion (H3O ) and a conjugate base anion (In ). This dissociation can be represented through the following equation and equilibrium expression: +- +- [H3 O ][In ] HIn (aq) + H23 O (l) H O (aq) + In (aq) Ka = weak acidhydronium conjugatebase [HIn] indicatorion indicator In order for a compound to be a useful indicator, the acidic form (HIn) and the basic form (In–) of the indicator should differ in color. Since equilibrium in acidic solution favors the formation of HIn, this species is called the acidic form of the indicator. Likewise, the In– form is called the basic form since it is favored in basic solutions. An equilibrium mixture of the indicator will be colored according to the relative concentration of each form of the indicator. The position of the equilibrium and, therefore, the relative + + concentration of the two forms of the indicator will depend on the H3O concentration, [H3O ] or in shorthand notation [H+]. The absorption curve of an indicator at different pH values can be studied to determine the equilibrium constant of the indicator. In this experiment, we will determine the equilibrium constant of bromocresol green (BCG).
    [Show full text]
  • (A) Fill in the Blanks : (1) 10% Nacl Is Known As Brine. 1 (2) Very Fine Particles Mainly Scatter Blue Light
    MT 2017 ___ ___ 1100 MT - SCIENCE & TECHNOLOGY - I (72) - SEMI PRELIM - I : PAPER - 3 Time : 2 Hours Semi Prelim - I : Model Answer Paper Max. Marks : 40 SECTION - A A.1. (A) Fill in the blanks : (1) 10% NaCl is known as brine. 1 (2) Very fine particles mainly scatter blue light. 1 (3) The phenomenon of change in the direction of light when it passes 1 from one transparent medium to another is called refraction. A.1. (B) True or False : (1) False : Salts of strong acid and weak base are acidic in nature. 1 (2) True 1 A.2. Rewrite the following statements by selecting the correct alternative: (1) (d) Lichen 1 (2) (b) Ferrous chloride 1 (3) (c) passes without bending 1 (4) (a) 50º 1 (5) (a) increases 1 A.3. Answer the following in short : (Any 5) (1) Washing soda Baking soda 2 (i) It is sodium carbonate. (i) It is sodium bicarbonate or sodium hydrogen carbonate. (ii) It's molecular formula is (ii) It's molecular formula is . Na2CO3 10H2O NaHCO3. (iii) It is a crystalline substance. (iii) It is an amorphous powder. (iv) It is used in manufacturing (iv) It is used in bakery for soaps and detergent. making cakes and bread lighter and spongy. .. 2 .. PAPER 3 (2) (i) Baking soda is chemically known as sodium bicarbonate. 2 (ii) On heating, sodium bicarbonate decomposes to form sodium carbonate, water and carbon dioxide (CO2). (iii) The carbon dioxide produced is released due to which the cake becomes soft and spongy. (iv) Hence, baking soda is used to make cake spongy and soft.
    [Show full text]
  • LESSON 3 WHAT IS Ph? LESSON 3 : WHAT IS Ph?
    ENVIRONMENTAL CHEMISTRY AND OCEAN ACIDIFICATION LESSON 3 WHAT IS pH? LESSON 3 : WHAT IS pH? LESSON OBJECTIVES We are learning about how acids and alkalis are identified using the pH scale. 1 2 3 4 IDENTIFY DETERMINE EXPLAIN ANALYZE what the pH the pH of some various ways to the pH of water scale is and the everyday identify the pH samples using purpose for it substances of substances universal indicator pa IN PARTNERSHIP WITH SPONSORED BY LESSON 3 : WHAT IS pH? KEY VOCABULARY Acid A substance with a pH of less than 7 Alkali A substance with a pH of more than 7 (A soluble base) Base A substance which can neutralize an acid Litmus test A test for acidity or alkalinity using litmus Neutral Solution A substance with the pH of 7 pH A scale (0 -14) which measures the acidity or alkalinity of a solution. A solution or paper that changes color gradually over a range of pH. Universal indicator This is used to test the acidity and alkalinity of a solution. IN PARTNERSHIP WITH SPONSORED BY 1 LESSON 3 : WHAT IS pH? STARTER Take a look at these four images. Think about what substances are shown in each image. How would you categorize these images into two groups? Why did you choose to organize them this way? Explain. IN PARTNERSHIP WITH SPONSORED BY 1 LESSON 3 : WHAT IS pH? STARTER Scientists group these substances into acids and alkalis. Acids Alkalis Acids are corrosive substances. Alkalis are also corrosive substances. They are sour to taste. They feel very slippery when touched.
    [Show full text]
  • Intermediate Answer Key Chapter 21: Acids and Bases
    CK-12 Chemistry Concepts - Intermediate Answer Key Chapter 21: Acids and Bases 21.1 Properties of Acids Practice Questions Watch the video at the link below and answer the following questions: http://www.youtube.com/watch?v=uahCEZf831c 1. Which of the four solutions are acids? 2. Stop the video at 0:30 minutes and predict conductivities. 3. What color did the acids turn when universal indicator was added? Answers 1. HCl and CH3COOH (acetic acid) 2. The acids and NaCl are ionized and will conduct electricity. 3. Pink Review Questions 1. Are all acids electrolytes in water? 2. What color does blue litmus turn in the presence of an acid? 3. What does the reaction of an acid and a base produce? Answers 1. Yes. 2. Red. 3. Water and a salt. 21.2 Properties of Bases Practice Questions Read the material at the site below and answer the following questions: 1 https://sites.google.com/site/sodiumhydroxsite/Acidsandbasesbasics/chemical- properties-of-bases 1. What does the reaction between an acid and a base produce? 2. What is this reaction called? 3. What does the reaction of a base with an ammonium salt form? Answers 1. A salt and water. 2. Neutralization. 3. A metal salt, ammonia, and water. Review Questions 1. Are bases electrolytes? 2. What color does a base turn phenolphthalein? 3. Do bases react with metals the same way that acids do? Answers 1. Yes, some are strong electrolytes and some are weak. 2. Red. 3. No. 21.3 Arrhenius Acids Practice Questions Read the material at the link below and answer the following questions: http://dwb4.unl.edu/Chem/CHEM869R/CHEM869RLinks/www.nidlink.com/7Ejfromm/arr henius.htm 1.
    [Show full text]
  • Universal Indicator, Bogens in Alcohol Safety Data Sheet According to Federal Register / Vol
    Universal Indicator, Bogens in Alcohol Safety Data Sheet according to Federal Register / Vol. 77, No. 58 / Monday, March 26, 2012 / Rules and Regulations Date of issue: 04/25/2014 Revision date: 05/15/2018 Supersedes: 04/25/2014 Version: 1.1 SECTION 1: Identification 1.1. Identification Product form : Mixtures Product name : Universal Indicator, Bogens in Alcohol Product code : LC26500 1.2. Recommended use and restrictions on use Use of the substance/mixture : For laboratory and manufacturing use only. Recommended use : Laboratory chemicals Restrictions on use : Not for food, drug or household use 1.3. Supplier LabChem Inc Jackson's Pointe Commerce Park Building 1000, 1010 Jackson's Pointe Court Zelienople, PA 16063 - USA T 412-826-5230 - F 724-473-0647 [email protected] - www.labchem.com 1.4. Emergency telephone number Emergency number : CHEMTREC: 1-800-424-9300 or +1-703-741-5970 SECTION 2: Hazard(s) identification 2.1. Classification of the substance or mixture GHS-US classification Flammable liquids H225 Highly flammable liquid and vapour Category 2 Serious eye damage/eye H319 Causes serious eye irritation irritation Category 2A Specific target organ H336 May cause drowsiness or dizziness toxicity (single exposure) Category 3 Full text of H statements : see section 16 2.2. GHS Label elements, including precautionary statements GHS-US labeling Hazard pictograms (GHS-US) : GHS02 GHS07 Signal word (GHS-US) : Danger Hazard statements (GHS-US) : H225 - Highly flammable liquid and vapour H319 - Causes serious eye irritation H336 - May cause drowsiness or dizziness Precautionary statements (GHS-US) : P210 - Keep away from heat, hot surfaces, open flames, sparks.
    [Show full text]
  • Summary Sheets 7F Hazards ● a Hazard Is Something That Can Cause Harm
    Summary Sheets 7F Hazards ● A hazard is something that can cause harm. ● Chemicals are labelled with hazard symbols to warn people of potential dangers. ● Some common hazard symbols are: Risk WS ● A risk is the chance that a hazard will actually cause harm. ● Risks can be reduced by taking precautions. E.g. wearing eye protection to prevent chemicals splashing in your eyes or tying long hair back to prevent it catching fire in a Bunsen flame. Acids ● Common substances at home that contain acids include: citric acid, vinegar, fizzy drinks and car battery acid. ● Acids have a sour taste. ● Most concentrated acids are corrosive. If they are added to water they become more dilute. Dilute acids are less hazardous. Many dilute acids are irritant. Alkalis ● Common substances at home that contain alkalis include: toothpaste, drain cleaner, oven cleaner. ● Many alkalis are metal hydroxide solutions. ● An alkali can be described as a soluble base. A base is any substance, soluble or insoluble, that neutralises an acid forming a salt and water. Indicators ● Indicators change colour and can be used to detect acids, alkalis and neutral solutions. ● Litmus is a common indicator. Solution Colour of litmus acid red neutral purple alkali blue Page 1 of 3 © Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 14 Summary Sheets 7F pH scale ● A numbered scale from 1 to 14. ● Acids have a pH less than 7. The lower the pH, the more acidic the substance is. The lower the pH, the more hazardous the acid is.
    [Show full text]
  • Universal Indicator Solution
    Safety Data Sheet Bogen Universal Indicator Solution Section 1 Product Description Product Name: Bogen Universal Indicator Solution Recommended Use: Science education applications Synonyms: Universal pH Indicator Distributor: Carolina Biological Supply Company 2700 York Road, Burlington, NC 27215 1-800-227-1150 Chemical Information: 800-227-1150 (8am-5pm (ET) M-F) Chemtrec: 800-424-9300 (Transportation Spill Response 24 hours) Section 2 Hazard Identification Classification of the chemical in accordance with paragraph (d) of §1910.1200; DANGER Flammable liquid and vapor. May cause cancer. Causes damage to organs. Toxic to aquatic life. GHS Classification: Carcinogenicity Category 1A, Specific Target Organ Systemic Toxicity (STOT) - Single Exposure Category 1, Hazardous to the aquatic environment - Acute Category 2, Flammable Liquid Category 3 Other Safety Precautions: IF exposed: Call a POISON CENTER or doctor/physician. IF exposed or concerned: Get medical advice/attention. Section 3 Composition / Information on Ingredients Chemical Name CAS # % Water 7732-18-5 52.36 Ethyl alcohol 64-17-5 42.95 Isopropyl Alcohol 67-63-0 2.4 Methanol 67-56-1 2.15 Phenolphthalein 77-09-8 0.06 Bromothymol Blue, Sodium Salt 34722-90-2 0.06 Methyl Red 493-52-7 0.02 Section 4 First Aid Measures Emergency and First Aid Procedures Inhalation: In case of accident by inhalation: remove casualty to fresh air and keep at rest. Eyes: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. Skin Contact: IF ON SKIN (or hair): Remove/Take off immediately all contaminated clothing. Rinse skin with water/shower. Ingestion: If swallowed, do not induce vomiting: seek medical advice immediately and show this container or label.
    [Show full text]
  • Acids and Bases the Voyage of the Proton
    UNIT 10 Acids and Bases The Voyage of the Proton Unit Overview This unit introduces the key concepts of acids and bases. The acidity of a solution is a measure- ment of the concentration of hydrogen ions it contains, and the acidity has a great impact on the properties of the solution. Pure water contains a certain concentration of hydrogen ions. Dissolving acids in water raises the concentration of hydrogen ions, while dissolving bases in water lowers the concentration. Acidity is measured in pH units, and the acidity of a solution depends both on the concentration of acid dissolved and the strength (degree of dissociation) of the acid. Chemists use indicators to measure pH as well as titration to determine the concentration and strength of an acid. Learning Objectives and Applicable Standards Participants should be able to: 1. Explain the dissociation of water molecules into hydronium and hydroxide ions and explain the equilibrium constant (K ) for that reaction. w 2. Define acids and bases using the Arrhenius and Brønsted-Lowry (conjugate acid/base pairs) definitions of acids and bases. 3. Explain acid dissociation constants (K ). Define the pK of an acid and understand its a a relationship to the acid’s strength. 4. Write the chemical equation for neutralization reactions. 5. Calculate the pH of a solution. 6. Explain the titration curves of monoprotic acids. 7. Define acid/base indicators and explain their uses. 8. Definebuffer and explain how one works. Key Concepts and People 1. Acids and Bases: An Arrhenius acid is defined as a molecule that when dissolved in water, increases the concentration of H+ ions.
    [Show full text]
  • Rainbow in a Tube Use a Ph Indicator to Create a Chemical Rainbow Lesson Plan
    Rainbow in a Tube Use a pH indicator to create a chemical rainbow Lesson Plan Description: Visitors create “rainbows” in clear acrylic tubing, using universal indicator, a dilute solution of acid, and a dilute solution of base. Audience: Hands-on activity for families and children ages 8 and up Length: 20 minutes Learning Objectives Visitors learn: • Chemicals (including common household products) can be acids, bases, or neutral. • Acids and bases have characteristic properties. • When acids and bases react they can cancel each other out, in a process called neutralization. • Scientists measure acids and bases using the pH scale. • pH indicator is used to measure the pH of a chemical. Visitors develop skills related to chemistry and science, including: • Developing and testing predictions • Observing, communicating and discussing experimental results Learning Standards National Science Education Standards 1. Science as Inquiry K-4: Abilities necessary to do scientific inquiry K-4: Understanding about scientific inquiry 5-8: Abilities necessary to do scientific inquiry 5-8: Understanding about scientific inquiry 9-12: Abilities necessary to do scientific inquiry 9-12: Understanding about scientific inquiry 2. Physical Science K-4: Properties of objects and materials 5-8: Properties and changes of properties in matter 9-12: Chemical reactions Sciencenter, Ithaca, NY Page 1 www.sciencenter.org Rainbow in a Tube Lesson Plan Background Information When most people hear the word “acid,” they think of something very dangerous that can dissolve metal and burn skin. In fact, many acids are not dangerous at all. Some are even found in the foods we eat! Any food that tastes sour is acidic.
    [Show full text]
  • CHEMISTRY's RAINBOW: the POWER of Ph
    TEACHER GUIDE CHEMISTRY'S RAINBOW: THE POWER OF pH MATERIALS PER GROUP: • Water • Citric acid (C6H8O7) • Sodium carbonate (Na2CO3) • Universal indicator • Universal indicator color chart BASE • Nine small (3 oz.) clear plastic cups • Two mini-scoops • Two plastic pipettes • Plastic beaker (90 mL) • One quart-sized Ziploc® bag • Alka-Seltzer® tablet NEUTRAL TOTAL DURATION: 20-30 min. pre-lab prep time; 40-50 min. class time ACID LESSON OBJECTIVES: Students will be able to: 1. Use the pH scale to classify solu- tions as acids or bases. 2. Neutralize an acid and a base. LESSON OVERVIEW: 3. Determine the relative concen- In chemistry, pH is a measure of the acidity or basicity of an aque- trations of hydrogen ions in a ous solution. The concentration (or amount) of hydrogen ions (H+) solution. present in a solution determines whether the solution is acidic or basic; acidic solutions have more H+ and basic (or alkaline) solu- tions have fewer H+. ESSENTIAL QUESTION: What is the relationship of acids and bases in nature? An education and outreach program of: TOPICAL ESSENTIAL QUESTION: Can the pH of a solution be altered? Noble Research Institute, LLC • 2510 Sam Noble Parkway • Ardmore, OK 73401 • www.noble.org • 580-223-5810 TEACHER GUIDE CHEMISTRY'S RAINBOW: THE POWER OF pH STANDARDS: Middle School Science and Engineering Practices: MS-PS1-2 1. Asking questions Students who demonstrate 2. Developing and using models understanding can: Analyze and interpret data on 3. Planning and carrying out investigations the properties of substances 4. Analyzing and interpreting data before and after the substances 5.
    [Show full text]
  • Acidic Properties of CO2 in Aqueous Solutions
    WARNING NOTICE The experiments described in these materials are potentially hazardous. Among other things, the experiments should include the following safety measures: a high level of safety training, special facilities and equipment, the use of proper personal protective equipment, and supervision by appropriate individuals. You bear the sole responsibility, liability, and risk for the implementation of such safety procedures and measures. MIT and Dow shall have no responsibility, liability, or risk for the content or implementation of any of the material presented. Legal Notice Acidic Properties of CO2 in Aqueous Solutions © Wendy Maeda/The Boston Globe. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse. Abstract A series of 2000 mL graduated cylinders are filled with colored solutions and several small pieces of solid dry ice (CO2) are gently added to the cylinders. Almost immediately the colors of the liquids begin to change, some slowly over a period of a few minutes, others more quickly, and some exhibiting several color changes one after the other. Materials Solid Dry Ice Dry Ice Container 6- 2000 mL graduated cylinders scooper for dry ice 6- 1 L plastic storage bottles Universal Indicator Bromothymol blue Phenolphthalein Ethanol 3',3"-dibromothymolsulfonephthalein Sodium Hydroxide Solution 6 – 100 mL stock bottles Insulated Gloves Safety Solid dry ice sublimes at -78 0C. Contact with the bare skin causes frostbite. Always use insulated gloves and wear safety goggles when handling it. Special care should be taken in handling the indicators, which could be potentially very hazardous if ingested, and cause irritation if they contact the skin or are inhaled.
    [Show full text]
  • Spectrophotometric Determination of the Pka, Isosbestic Point and Equation of Absorbance Vs
    American Journal of Analytical Chemistry, 2014, 5, 1290-1301 Published Online December 2014 in SciRes. http://www.scirp.org/journal/ajac http://dx.doi.org/10.4236/ajac.2014.517135 Spectrophotometric Determination of the pKa, Isosbestic Point and Equation of Absorbance vs. pH for a Universal pH Indicator L. E. Vidal Salgado, C. Vargas-Hernández Laboratory of Optical Properties of Materials (POM), National University of Colombia, Manizales, Colombia Email: [email protected] Received 3 October 2014; revised 20 November 2014; accepted 7 December 2014 Copyright © 2014 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract The pKa and the isosbestic point of the universal pH indicator Carlo Ebra 1-11 (catalog number 45712) were determined using UV-Vis spectrophotometry. Aqueous buffer solutions with pHs ranging from 3.83 to 10.85 were mixed. Four methods—two graphical and two mathematical— were used to estimate the acid dissociation constant (pKa) and isosbestic point using absorbance measurements. The equation for the dependence of the absorbance on pH at λ = 600 nm was ob- tained using calibration curves. The resulting average pKa of the four methods was 8.277 with a standard deviation of 0.1728. The results obtained using the mathematical methods were very similar, with a deviation of 0.0014; the average pKa determined using these methods was 8.263 ± 0.001. The literature contains no previous reports of the pKa of this indicator. The isosbestic point occurs at a wavelength of 494 nm, with an absorbance of 0.46.
    [Show full text]