LABORATORY MANUAL FOR CHEMISTRY 102 Prepared by Department of Chemistry and Physics Los Angeles Valley College This Lab Book Belongs To: Copyright © 2015 by the Department of Chemistry and Physics, Los Angeles Valley College. All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means, electronic or otherwise, or stored in a database or retrieval system, without written permission of the copyright holder. 2 TABLE OF CONTENTS Contents LABORATORY SAFETY RULES .................................................................................................................. 3 FACTORS AFFECTING THE RATE OF A REACTION .................................................................................... 6 CHEMICAL KINETICS ............................................................................................................................. 13 LE CHÂTELIER'S PRINCIPLE ................................................................................................................... 25 WEAK ACIDS AND BASES ...................................................................................................................... 35 DETERMINATION OF Ka BY pH TITRATION ............................................................................................ 43 BUFFERS AND pH ................................................................................................................................. 53 ACID-BASE EQUILIBRIUM PROBLEMS .................................................................................................. 61 A SOLUBILITY INVESTIGATION .............................................................................................................. 66 SOLUBILITY AND Ksp DETERMINATION ................................................................................................. 73 DETERMINATION OF Kf BY SPECTROPHOTOMETRIC METHODS ........................................................... 81 Ksp, G, H, AND S OF POTASSIUM NITRATE DISSOLVING IN WATER ............................................ 89 DETERMINATION OF PERCENT OXALATE BY OXIDATION-REDUCTION TITRATION ............................. 97 ELECTROCHEMISTRY .......................................................................................................................... 105 ELECTROLYTIC DETERMINATION OF THE MOLAR MASS OF LEAD ...................................................... 117 DETERMINATION OF THE HALF-LIFE OF POTASSIUM-40 .................................................................... 121 COORDINATION COMPOUNDS AND COMPLEX IONS ......................................................................... 127 EQUILIBRIUM BETWEEN TWO COMPLEX IONS OF Co2+ IN SOLUTION .............................................. 130 SYNTHESIS AND ANALYSIS OF A NICKEL COMPLEX ............................................................................ 141 MOLECULAR MODELS OF TRANSITION METAL COMPLEXES ............................................................. 151 APPENDIX A ........................................................................................................................................ 155 APPENDIX B ........................................................................................................................................ 156 APPENDIX C ........................................................................................................................................ 166 3 LABORATORY SAFETY RULES Note: Failure to follow safety rules will result in expulsion from this course. 1. Wear approved safety goggles at all times in the laboratory. 2. It is not advisable to wear contact lenses during lab. 3. Do not wear loose clothing to lab. It is a fire hazard. 4. Tie back long hair. It too is a fire hazard. 5. Wear closed shoes to lab. 6. Never put anything into your mouth while in the lab. 7. Immediately wash off any chemicals spilled on your skin or clothes. 8. Keep the lab neat. Return reagent containers and equipment to proper locations. Put any belongings not needed for experimental work on the shelves provided. 9. Clean up all chemical spills or broken glass immediately. 10. Think about how much chemical you will need before you take it from a stock (reagent) bottle. Never return unused chemicals to stock bottles. Never dip into a reagent bottle with anything (spatula, dropper, pipet, etc.)! 11. Dispose of waste chemicals only as instructed. 12. Behave in a responsible manner. 13. You should be aware of the location and use of laboratory safety equipment. 14. Immediately report accidents and injuries to your professor. 15. Do not perform unauthorized experiments. 16. Thoroughly wash your hands any time you leave the lab. 17. No smoking on the Los Angeles Valley College campus. I have carefully read all of the safety precautions summarized above and recognize that it is my responsibility to observe them throughout this course. Chemistry 102 Printed Name Date Section Number Signature 4 5 LABORATORY SAFETY RULES Note: Failure to follow safety rules will result in expulsion from this course. 1. Wear approved safety goggles at all times in the laboratory. 2. It is not advisable to wear contact lenses during lab. 3. Do not wear loose clothing to lab. It is a fire hazard. 4. Tie back long hair. It too is a fire hazard. 5. Wear closed shoes to lab. 6. Never put anything into your mouth while in the lab. 7. Immediately wash off any chemicals spilled on your skin or clothes. 8. Keep the lab neat. Return reagent containers and equipment to proper locations. Put any belongings not needed for experimental work on the shelves provided. 9. Clean up all chemical spills or broken glass immediately. 10. Think about how much chemical you will need before you take it from a stock (reagent) bottle. Never return unused chemicals to stock bottles. Never dip into a reagent bottle with anything (spatula, dropper, pipet, etc.)! 11. Dispose of waste chemicals only as instructed. 12. Behave in a responsible manner. 13. You should be aware of the location and use of laboratory safety equipment. 14. Immediately report accidents and injuries to your professor. 15. Do not perform unauthorized experiments. 16. Thoroughly wash your hands any time you leave the lab. 17. No smoking on the Los Angeles Valley College campus. Come to lab prepared!! Carefully read the experiment before coming to lab. 6 FACTORS AFFECTING THE RATE OF A REACTION INTRODUCTION There are several factors that affect the rate of a reaction. Some of these factors are: • Mixing • Concentration of a reactant • Temperature • The presence of a catalyst • Surface area in a heterogeneous reaction In this experiment we will examine these factors. This experiment is an introduction to the more commonly encountered factors that affect the rate of reactions. There are other factors that do influence the rate of a reaction such as light, molecular geometry and the type of solvent used; however, we do not have the time to explore all facets of all factors that affect reaction rate. PROCEDURE A. The effect of mixing. 1. Fill two small test tubes ¼ full with water. 2. Into each tube add a small crystal of solid potassium permanganate. 3. Let one tube sit undisturbed. Swirl the other tube to dissolve the potassium permanganate. Note the amount of time it takes the swirled sample to dissolve (form a solution). 4. Continue with the experiment (Parts B through E) and observe the undisturbed tube every few minutes. Note approximately how long it takes for the potassium permanganate to dissolve and diffuse throughout this tube. To complete Parts B and C each group will need a timer, a total of 7.0 mL of 3%(m/m) hydrogen peroxide solution (H2O2) and a total of 15.0 mL of solution A (a mixture of starch (as an indicator), acetic acid, potassium iodide, and sodium thiosulfate). Do not waste reagents by taking more than you need for the experiment! B. The effect of concentration of a reactant. 1. In your smallest beaker place 5.0 mL of solution A and add 5.0 mL of the hydrogen peroxide solution. Start your timer as soon as the solutions are mixed in the beaker. 2. Record the number of seconds that elapse until the solution turns blue/black. 3. Repeat steps 1 and 2 using 5.0 mL of solution A and 4.0 mL of deionized water which has been added to 1.0 mL of the hydrogen peroxide solution. 7 C. The effect of temperature. 1. Place a test tube containing 5.0 mL of solution A and another test tube containing 4.0 mL of deionized water combined with 1.0 mL of the 3% hydrogen peroxide solution into a warm water bath for about 5 minutes. 2. Measure the temperature of the water bath. 3. Mix the two solutions into a small beaker and start your timer. 4. Record the number of seconds required for the solution to turn blue/black. 5. Compare this number with the elapsed time from the second (diluted) mixture in part B. D. The effect of a catalyst. 1. Fill a large (400 mL or larger) beaker about 2/3 full with water. 2. Fill a small test tube all the way with water. Place your finger over the opening and invert it into the beaker. Do not allow any gas to enter the tube as you remove your finger. 3. Obtain a gas collection apparatus. Place the gas evolution tube under the inverted test tube in the beaker. 4. Do you notice gas formation in the 3% H2O2 reagent bottle? 5. Place 20 drops of 3 M copper(II) nitrate solution in the flask. Swirl the contents of the flask. Is any gas formed in the catalyst solution alone? 6. Quickly add about 20 mL of 3% hydrogen peroxide solution