Glencoe Chemistry: Matter and Change. CBL Lab Manual

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CBL Laboratory Manual Student Edition

A Glencoe Program

Hands-On Learning: Laboratory Manual, SE/TE Forensics Laboratory Manual, SE/TE CBL Laboratory Manual, SE/TE Small-Scale Laboratory Manual, SE/TE ChemLab and MiniLab Worksheets Review/Reinforcement: Study Guide for Content Mastery, SE/TE Solving Problems: A Chemistry Handbook Reviewing Chemistry Guided Reading Audio Program Applications and Enrichment: Challenge Problems Supplemental Problems

Teacher Resources: Lesson Plans Block Scheduling Lesson Plans Spanish Resources Section Focus Transparencies and Masters Math Skills Transparencies and Masters Teaching Transparencies and Masters Solutions Manual Technology: Chemistry Interactive CD-ROM Vocabulary PuzzleMaker Software, Windows/MacIntosh Glencoe Science Web site: science.glencoe.com

Assessment: Chapter Assessment MindJogger Videoquizzes (VHS/DVD) Computer Test Bank, Windows/MacIntosh

Copyright © by The McGraw-Hill Companies, Inc. All rights reserved. Permission is granted to reproduce the material contained herein on the condition that such material be reproduced only for classroom use; be provided to students, teachers, and families without charge; and be used solely in conjunction with the Chemistry: Matter and Change program. Any other reproduction, for use or sale, is prohibited without prior written permission of the publisher. Send all inquiries to: Glencoe/McGraw-Hill 8787 Orion Place Columbus, OH 43240-4027 ISBN 0-07-824530-3 Printed in the United States of America. 1 2 3 4 5 6 7 8 9 10 045 09 08 07 06 05 04 03 02 01

CBL LABORATORY MANUAL

Contents To the Student . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Organization of Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Sending Data to Graphical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . v CBL Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Safety in the Laboratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi Safety Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.

Laboratory Activities 1

Quantitative and Qualitative Observations . . . . . . . . . . . . . . . . . 1

2

Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3

Melting and Freezing Points . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4

Boyle’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5

Gay-Lussac’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6

Determining Molar Mass Using Freezing Point Depression . . . 21

7

Calorimetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

8

Hess’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

9

Determine the Molar Mass of an Unknown Acid . . . . . . . . . . . 33

10 Reaction Potentials of Metals . . . . . . . . . . . . . . . . . . . . . . . . . 37

CBL Laboratory Manual

Chemistry: Matter and Change

iii

To the Student Chemistry is the science of matter, its properties, and changes. In your classroom work in chemistry, you will learn a great deal about the information that has been gathered by scientists about matter. But, chemistry is not just information. It is also a process for finding out more about matter and its changes. Laboratory activities are the primary means that chemists use to learn more about matter. The activities in the CBL Laboratory Manual require that you form and test hypotheses, measure and record data and observations, analyze those data, and draw conclusions based on those data and your knowledge of chemistry. These processes are the same as those used by professional chemists and all other scientists. CBL (computer-based laboratory) activities use graphing calculators to collect and analyze real-world data using different probes or sensors. The CBL system is an interface that collects data from the probes and sends the information to the calculator. The calculator, in turn, runs stored data collection and processing programs, which interpret and plot data obtained from the CBL system.

• Introduction Following the title and number of each activity, an introduction provides a background discussion about the problem you will study in the activity. • Problem The problem to be studied in this activity is clearly stated. • Objectives The objectives are statements of what you should accomplish by doing the investigation. Recheck this list when you have finished the activity. • Materials The materials list shows the apparatus you need to have on hand for the activity. • Safety Precautions Safety symbols and statements warn you of potential hazards in the laboratory. Before beginning any activity, refer to page vii to see what these symbols mean. • Pre-Lab The questions in this section check your knowledge of important concepts needed to complete the activity successfully. • Procedure The numbered steps of the procedure tell you how to carry out the activity and sometimes offer hints to help you be successful in the laboratory. Some activities have CAUTION statements in the procedure to alert you to hazardous substances or techniques. • Hypothesis This section provides an opportunity for you to write down a hypothesis for this activity. • Data and Observations This section presents a suggested table or form for collecting your laboratory data. Always record data and observations in an organized way as you do the activity. • Analyze and Conclude The Analyze and Conclude section shows you how to perform the calculations necessary for you to analyze your data and reach conclusions. It provides questions to aid you in interpreting data and observations in order to reach an experimental result. You are also asked to form a scientific conclusion based on what you actually observed, not what “should have happened.” An opportunity to analyze possible errors in the activity is also given. • Real-World Chemistry The questions in this section ask you to apply what you have learned in the activity to other real-life situations. You may be asked to make additional conclusions or research a question related to the activity. iv




Organization of Activities


Sending Data to Graphical Analysis If using the TI-83 graphing calculator: 1. On the TI calculator, press 2nd Link, then select 4:List… from the SEND menu. 2. Use the down arrow to locate the lists on the SELECT menu. Position the arrow in front

of a list you want to send to GRAPHICAL ANALYSIS and press ENTER to select that particular list. More than one list may be selected in this manner. A filled box will appear beside each list that will be sent. To deselect, press ENTER. The filled-in box will disappear. 3. Press the right arrow on the calculator, then select 1:TRANSMIT. The lists will appear in columns in the data table window of GRAPHICAL ANALYSIS. They will be labeled with simple list names from the calculator. If you want to rename the lists or add units, doubleclick on the column heading and enter a new name or label in the dialog box. If using another type of TI graphing calculator with a PC computer: 1. Connect the TI-graph link cable to a free serial port of the Windows computer and to the

port on the bottom edge of the TI calculator. 2. With GRAPHICAL ANALYSIS running, choose Import from the TI Calculator under the FILE MENU. If the TI-graph link cable is not connected to the serial port designated in the status box, click on SELECT PORT and choose the correct port for the TI-graph link cable.


CBL Equipment This diagram shows the basic equipment used in most of these CBL activities. Such equipment includes the CBL unit, a graphing calculator, link cable, AC adapter for the CBL unit, DIN adapter (needed for some probes), and a probe or sensor.

DIN adapter TI-83 calculator

CBL unit Gas pressure sensor

Syringe

AC adapter Link cable



v


Safety in the Laboratory The chemistry laboratory is a place to experiment and learn. You must assume responsibility for your own personal safety and that of people working near you. Accidents are usually caused by carelessness, but you can help prevent them by closely following the instructions printed in this manual and those given to you by your teacher. The following are some safety rules to help guide you in protecting yourself and others from injury in a laboratory.

2. Study your lab activity before you come to the lab. If you are in doubt about any procedures, ask your teacher for help. 3. Safety goggles and a laboratory apron must be worn whenever you work in the lab. Gloves should be worn whenever you use chemicals that cause irritations or can be absorbed through the skin. 4. Contact lenses should not be worn in the lab, even if goggles are worn. Lenses can absorb vapors and are difficult to remove in an emergency. 5. Long hair should be tied back to reduce the possibility of it catching fire. 6. Avoid wearing dangling jewelry or loose, draping clothing. The loose clothing may catch fire and either the clothing or jewelry could catch on chemical apparatus. 7. Wear shoes that cover the feet at all times. Bare feet or sandals are not permitted in the lab. 8. Know the location of the fire extinguisher, safety shower, eyewash, fire blanket, and first-aid kit. Know how to use the safety equipment provided for you. 9. Report any accident, injury, incorrect procedure, or damaged equipment immediately to your teacher. 10. Handle chemicals carefully. Check the labels of all bottles before removing the contents. Read the labels three times: before you pick up the container, when the container is in your hand, and when you put the bottle back. 11. Do not return unused chemicals to reagent bottles. 12. Do not take reagent bottles to your work area unless specifically instructed to do so. Use test tubes, paper, or beakers to obtain your chemicals.

vi


Take only small amounts. It is easier to get more than to dispose of excess. 13. Do not insert droppers into reagent bottles. Pour a small amount of the chemical into a beaker. 14. Never taste any chemical substance. Never draw any chemicals into a pipette with your mouth. Eating, drinking, chewing gum, and smoking are prohibited in the laboratory. 15. If chemicals come into contact with your eyes or skin, flush the area immediately with large quantities of water. Immediately inform your teacher of the nature of the spill. 16. Keep combustible materials away from open flames. (Alcohol and acetone are combustible.) 17. Handle toxic and combustible gases only under the direction of your teacher. Use the fume hood when such materials are present. 18. When heating a substance in a test tube, be careful not to point the mouth of the tube at another person or yourself. Never look down the mouth of a test tube. 19. Use caution and the proper equipment when handling hot apparatus or glassware. Hot glass looks the same as cool glass. 20. Dispose of broken glass, unused chemicals, and products of reactions only as directed by your teacher. 21. Know the correct procedure for preparing acid solutions. Always add the acid slowly to the water. 22. Keep the balance area clean. Never weigh chemicals directly on the pan of the balance. 23. Do not heat graduated cylinders, burettes, or pipettes with a laboratory burner. 24. After completing an activity, clean and put away your equipment. Clean your work area. Make sure the gas and water are turned off. Wash your hands with soap and water before you leave the lab.



1. The chemistry laboratory is a place for serious work. Do not perform activities without your teacher’s permission. Never work alone in the laboratory. Work only when your teacher is present.

CBL LABORATORY MANUAL The Chemistry: Matter and Change program uses safety symbols to alert you and your students to possible laboratory dangers. These symbols are provided in the student text in Appendix B and are explained below. Be sure your students understand each symbol before they begin an activity that displays a symbol.

SAFETY SYMBOLS

EXAMPLES

PRECAUTION

REMEDY

Special disposal procedures need to be followed.

certain chemicals, living organisms

Do not dispose of Dispose of wastes as these materials in directed by your the sink or trash can. teacher.

Organisms or other biological materials that might be harmful to humans

bacteria, fungi, blood, unpreserved tissues, plant materials

Avoid skin contact Notify your teacher if with these materials. you suspect contact Wear mask or gloves. with material. Wash hands thoroughly.

EXTREME TEMPERATURE

Objects that can burn skin by being too cold or too hot

boiling liquids, hot Use proper plates, dry ice, liquid protection when nitrogen handling.

SHARP OBJECT

Use of tools or glassware that can easily puncture or slice skin

razor blades, pins, scalpels, pointed tools, dissecting probes, broken glass

Practice commonGo to your teacher sense behavior and for first aid. follow guidelines for use of the tool.

Possible danger to respiratory tract from fumes

ammonia, acetone, nail polish remover, heated sulfur, moth balls

Make sure there is Leave foul area and good ventilation. notify your teacher Never smell fumes immediately. directly. Wear a mask.

DISPOSAL BIOLOGICAL

FUME

ELECTRICAL

IRRITANT Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.

HAZARD

CHEMICAL

TOXIC

OPEN FLAME

Eye Safety Proper eye protection should be worn at all times by anyone performing or observing science activities.


Go to your teacher for first aid.

Possible danger from improper grounding, electrical shock or liquid spills, short burn circuits, exposed wires

Double-check setup with teacher. Check condition of wires and apparatus.

Substances that can irritate the skin or mucus membranes of the respiratory tract

pollen, moth balls, steel wool, fiber glass, potassium permanganate

Wear dust mask and Go to your teacher gloves. Practice extra for first aid. care when handling these materials.

Chemicals that can react with and destroy tissue and other materials

bleaches such as hydrogen peroxide; acids such as sulfuric acid, hydrochloric acid; bases such as ammonia, sodium hydroxide

Wear goggles, gloves, and an apron.

Substance may be poisonous if touched, inhaled, or swallowed

mercury, many metal Follow your teacher’s compounds, iodine, instructions. poinsettia plant parts

Always wash hands thoroughly after use. Go to your teacher for first aid.

Open flame may ignite flammable chemicals, loose clothing, or hair

alcohol, kerosene, potassium permanganate, hair, clothing

Tie back hair. Avoid wearing loose clothing. Avoid open flames when using flammable chemicals. Be aware of locations of fire safety equipment.

Notify your teacher immediately. Use fire safety equipment if applicable.

Clothing Protection This symbol appears when substances could stain or burn clothing.

Animal Safety This symbol appears when safety of animals and students must be ensured.

Do not attempt to fix electrical problems. Notify your teacher immediately.

Immediately flush the affected area with water and notify your teacher.

Radioactivity This symbol appears when radioactive materials are used.


vii

Name

LAB

Date

1

Class

CBL LABORATORY MANUAL Use with Section 1.3

Quantitative and Qualitative Observations

R


eactions are taking place around you all the time. It is important to be aware of your surroundings and understand how humans interact with these surroundings. Your five senses allow you to observe the world in which you live. In the lab, you only use four senses to make observations. Nothing is ever tasted in the lab. Sometimes tools can extend your senses. When you describe the color, odor, or texture of an object, you are making a qualitative observation. Quantitative observations involve measured quantities, such as 15 g or 2.5 L. It is important not to confuse observations and interpretations in the lab. Observations are made using your senses; interpretations are proposed explanations that are based on observations. In this lab, you will be making both qualitative and quantitative observations.

Problem

Objectives

Materials

How many observations can you make about a reaction? Are your observations qualitative or quantitative?

• Measure the change in temperature related to a chemical reaction. • Compare quantitative observations and qualitative observations. • Discuss the difference between observations and interpretations. • Predict one product produced during the reaction.

CBL unit TI graphing calculator link cable temperature probe copper(II) chloride 2 2-in square of aluminum foil

150-mL beaker 100-mL graduated cylinder microspatula glass stirring rod paper towel magnifying glass weighing paper

Safety Precautions • • • •

Always wear safety goggles and a lab apron. Do not touch chemicals with bare skin. Do not inhale vapors that are released. Dispose of materials as your teacher instructs.

Pre-Lab 1. What is the difference between observations and

interpretations? 2. Give three examples of qualitative observations and three examples of quantitative observations. CBL Laboratory Manual

3. What are some tools that scientists use to enhance

their observational techniques?

Chemistry: Matter and Change • Chapter 1

1

Name

Date

1

CBL LABORATORY MANUAL 4. Using the 100-mL graduated cylinder, obtain

Procedure Part A: Preparing the CBL System 1. Connect the CBL unit to the temperature probe,

5.

as shown in Figure A. Make sure the temperature probe is in channel 1. Then, using a link cable, connect the CBL unit to the graphing calculator. 6. Figure A TI graphing calculator

CBL unit

Temperature probe

7. 8.

9. AC adapter Link cable

10. 2. Turn on the CBL unit and the graphing calcula-

tor. Press the PRGM button on the calculator and choose ChemBio from the list of programs. Press ENTER on the calculator twice. 3. Choose SET UP PROBES from the MAIN MENU. Enter 1 as the number of probes. On the SELECT PROBES menu, choose TEMPERATURE. Enter 1 as the channel number. 4. From the MAIN MENU, select COLLECT DATA. On the DATA COLLECTION menu, select TRIGGER/PROMPT. Part B: Collecting Data 1. Obtain a 2 2-in square of aluminum. 2. Place a small scoop of copper(II) chloride onto

a piece of weighing paper. 3. Make as many observations of the aluminum and the copper(II) chloride as possible. Record your observations in Data Table 1.

2


11.

12.

50 mL of distilled water. Pour the water into the 150-mL beaker. Place the temperature probe in the water. Record an initial temperature of the water by pressing TRIGGER on the CBL unit. Follow directions on the calculator to continue collecting data. With the temperature probe in the water, transfer the copper(II) chloride into the water without touching the probe. Try not to agitate the mixture. Note any temperature change. Before stirring the mixture, record as many observations as possible in Data Table 1. Using the glass stirring rod, stir the mixture. After stirring, make and record as many observations as possible. Roll the aluminum foil loosely into a ball. Do not tightly pack the aluminum. Place the foil ball in the copper(II) chloride mixture. Let the reaction proceed for about 15 min. Make and record as many observations as possible of the reaction mixture. Record the maximum temperature change that takes place during the reaction. When the reaction appears to be complete, remove the probe from the water. Pour off as much of the liquid as possible. Label a paper towel with your name and class period. Pour the remaining contents onto the paper towel. Set aside the paper towel for observation on the second day of lab.

Cleanup and Disposal 1. Disconnect the temperature probe from the

CBL unit. 2. After emptying the beaker, clean and rinse the beaker. Rinse the probe with distilled water and carefully wipe it dry. 3. Return all equipment to its proper place. 4. Clean up the lab area and wash your hands with soap or detergent before leaving the lab.



LAB

Class

Name

Date

LAB

1

Class


Data and Observations Data Table 1 Steps

Observations

3. Dry copper(II) chloride Aluminum

5. Initial temperature of water (°C) 7. Copper(II) chloride and water mixture before stirring

8. Copper(II) chloride and water mixture after stirring

9. Copper(II) chloride and water mixture with aluminum

10. Final temperature of mixture (°C)

Analyze and Conclude 1. Observing and Inferring Describe the events that took place that provide evidence for a Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.

chemical reaction.

2. Observing and Inferring Name one product that is formed in this reaction.

3. Observing and Inferring What observations did you make during this lab? What

interpretations can you make from your observations?

4. Thinking Critically Which of the observations you made were quantitative?



3

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Date

LAB

1

Class


5. Error Analysis What could be done to improve the accuracy of your measurements in

this activity?

Real-World Chemistry 1. Why is it important for scientists to have

3. How do observation and interpretation skills

help when working with the scientific method?


as much data as possible before making interpretations? 2. Why is important for high school students to develop their observation skills?

4



Name

LAB

Date

2

Class


Conductivity

T

he solubility of a substance describes the ability of one substance to dissolve in another substance. Water is used as a solvent to determine the solubility of various solids. Some substances dissolve in water; some substances do not. When dissolved in water, the ions in an ionic compound separate, or dissociate. As the ions dissociate, electrons are free to move about in the solution. As these electrons move, it is possible for them to carry an electric current.


In this activity, the conductivity of substances is used to determine to what extent substances dissociate in water. This lab compares an ionic solid to a nonionic substance and relates the effect of concentration on conductivity.

Problem

Objectives

Materials

How can an electric current be used to determine the extent to which solid substances dissolve in water?

• Predict what substances will dissociate in water based on their chemical makeup. • Write balanced equations for the dissociation of substances in water. • Compare the conductivity of various solutions. • Classify substances as nonionic or ionic. • Determine what effect concentration has on conductivity.

CBL unit TI graphing calculator computer link cable conductivity probe adapter cable dropper bottles (3) with: (a) 1M NaCl (b) 1M MgCl2 (c) 1M AlCl3 50-mL beakers (2) with: (a) NaCl (b) sugar (C12H22O11)

400-mL beaker 150-mL beakers (3) 100-mL graduated cylinder glass stirring rod ring stand with test-tube clamp wash bottle of distilled water microspatula electronic balance weighing dishes (2) plastic beral pipettes (3)

Safety Precautions • Always wear safety goggles and a lab apron. • Use caution when working with electricity. • The conductivity probe is fragile. Use caution when setting this up in the ring stand. • Never taste any chemical substances.



5

Name

Date

2

CBL LABORATORY MANUAL 4. Turn on the CBL unit and the graphing calculator.

Pre-Lab 1. Read over the entire laboratory activity. Write

balanced chemical equations for the dissociation of NaCl, MgCl2 and AlCl3 in water. Form a hypothesis as to which of these compounds would conduct the most electricity and the least electricity. Record your hypothesis on the next page. 2. Which of the following substances would be considered ionic? Which would be nonionic? Explain your reason for each answer. a. potassium chloride (KCl) b. methanol (CH3OH) c. glucose (C6H12O6) d. hydrochloric acid (HCl) e. zinc oxide (ZnO) 3. Sketch a diagram of NaCl dissolving in water.

Choose ChemBio from the list of programs. Press ENTER on the calculator twice. 5. Choose SET UP PROBES from the MAIN MENU. Enter 1 as the number of probes. On the SELECT PROBES menu, choose CONDUCTIVITY. Enter 1 as the channel number. Then select USE STORED from the CALIBRATION menu and select H 0-2000 MICS from the CONDUCTIVITY menu. Make sure the switch on the box is set to the same value. 6. From the MAIN MENU, select COLLECT DATA. On the DATA COLLECTION menu, select TRIGGER PROMPT. Allow the unit to warm up and then press ENTER. Part B: Comparing Ionic Compounds 1. Label three beral pipettes—NaCl, MgCl2, and

Procedure Part A: Preparing the CBL System If your teacher has the CBL system set up, you may skip to Part B. 1. Set up a ring stand, clamp, and CBL probe as illustrated in Figure A. 2. Plug the conductivity probe into the adapter cable in channel 1 of the CBL unit. 3. Connect the CBL unit to the graphing calculator with a link cable. Figure A

2.

3. 4.

Ring stand Conductivity probe

Test-tube clamp

5. Graphing calculator

CBL unit

Beaker

6.

7. Link cable

6


AlCl3. Fill one of the pipettes with the 1.0M solution of NaCl. Fill the other two pipettes with 1.0M MgCl2 and AlCl3, respectively. Using the 100-mL graduated cylinder, measure 70 mL of distilled water into the 150-mL beaker. Raise the beaker until the conductivity probe is in the water. After the conductivity meter stabilizes, press TRIGGER on the CBL unit. Measure and record the conductivity of the distilled water in Data Table 1. Lower the beaker and place 1 drop of NaCl solution into the distilled water. Stir with the glass stirring rod and then raise the beaker until the conductivity probe is in the solution. After the conductivity meter stabilizes, press TRIGGER on the CBL unit. Measure and record the conductivity of this solution in Data Table 1. Adding 1 more drop of the NaCl solution, repeat step 4. Continue adding 1 drop and recording its conductivity until a total of 8 drops of NaCl solution has been added. If a TI-83 graphing calculator is being used, or another type of graphing calculator and a computer is available, refer to Appendix A for instructions on how to convert this data into graphical analysis. After transferring the data to the graphing program, rinse out the beaker with distilled water and repeat steps 4–6 two more times using MgCl2 CBL Laboratory Manual


LAB

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Name

Date

LAB

2

Class


and AlCl3, respectively. Be sure to transfer the data to the graphing program and rinse out the beaker after each substance. Rinse the conductivity probe with distilled water in between each substance. (Do this by spraying the probe over the 400-mL beaker or sink.) Part C: Comparing Ionic and Molecular Substances

4. Use the conductivity probe to monitor the con-

ductivity of the sodium chloride solution. Record the conductivity in Data Table 2. 5. Rinse the probe with distilled water. 6. Use the conductivity probe to monitor the conductivity of the sucrose solution. Record the conductivity in Data Table 2.

Cleanup and Disposal

1. In two separate weighing dishes, measure 10 g

of sodium chloride (NaCl) and 10 g of sucrose (C12H22O11). 2. Using the 100-mL graduated cylinder, place 50 mL of distilled water in each of two 150-mL beakers. Label one of the beakers sodium chloride (NaCl) and the other beaker sucrose (C12H22O11). 3. Pour the solid sodium chloride and sucrose into the appropriate beakers and stir with a glass stirring rod.

1. Disconnect the conductivity probe from the CBL

unit. 2. Rinse the probes with distilled water. 3. Rinse out the beakers with distilled water. 4. Clean up your lab area and wash your hands. Replace the lab equipment to the appropriate area.

Hypothesis

Data and Observations Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.

Data Table 1 (to be used if graphing program not available) Drops

NaCl conductivity (microsiemens)

MgCl2 conductivity (microsiemens)

AlCl3 conductivity (microsiemens)

0 1 2 3 4 5 6 7 8

Data Table 2 Substance

Conductivity

Sodium chloride (NaCl) Sucrose (C12H22O11)



7

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LAB

2

Class


Analyze and Conclude 1. Observing and Inferring Which solution was the best conductor of electricity? Explain.

2. Making and Using Graphs Make a graph of conductivity versus concentration. Plot

conductivity on the y-axis and concentration (number of drops) on the x-axis. If you used a graphing program, you may use those graphs. Draw a line of best fit for each of these sets of data.

AlCl3, what is the ratio of number of electrons transferred in each reaction? How does this explain the graphs drawn in question 2?

4. Drawing a Conclusion How does the conductivity of sodium chloride compare with

sucrose? Why is this the case?

Real-World Chemistry What types of substances make good conductors of electricity? What element is used to bring electricity to the places where we live? Why is this an effective substance?

8




3. Observing and Inferring For each of the dissociation reactions of NaCl, MgCl2 and

Name

LAB

Date

3

Class


Melting and Freezing Points

Use with Section 13.4

W

hen you add heat to a substance, the average kinetic energy of the particles in the substance increases. If enough energy is added, the particles overcome the attractive forces holding the particles together and the substance changes state—from a solid to a liquid, or even to a gas. As this happens, the movement of the particles becomes more random. By contrast, as substances lose heat, the interactions between particles increases and the particles become more ordered.


The temperature of a substance stays the same during any change of state, or phase change. The energy absorbed by the system is used to overcome intermolecular attractions, not to increase the kinetic energy (temperature) of the substance. In this lab, you will determine the melting/freezing point for water and a food preservative, BHT (butylated hydroxytoluene, C15H24O).

Problem

Objectives

Materials

What are the melting/ freezing points of water and BHT (C15H24O)?

• Describe the process of melting and freezing. • Determine the melting and freezing points of two substances. • Predict which substance will have a higher or lower melting/freezing point.

CBL unit TI graphing calculator link cable temperature probe AC adapter BHT salt (NaCl) ice water

400-mL beaker 25-mL graduated cylinder 20 150-mm test tube hot plate ring stand clamp glass stirring rod

Safety Precautions • • • • •

Always wear safety goggles and a lab apron. Use caution when working with the hot plate. Never taste any of the chemicals used in the lab. Do not touch the salt–ice solution. It will be extremely cold. Dispose of materials as your teacher instructs.

Pre-Lab 1. Read the entire laboratory activity. Sketch a

representation of the solid, liquid, and gaseous states of matter. 2. What terms are used to describe the following phase changes: solid to liquid; liquid to gas; solid to gas; gas to liquid; liquid to solid?


3. Using your textbook, look up the heating curve

for water. Describe each portion of the curve and explain why it has that particular shape.


9

Name

Date

3

Procedure

CBL LABORATORY MANUAL 6. Now lower the test tube of water into the beaker

Part A: Preparing the CBL System 1. Connect the CBL unit to the temperature probe,

as shown in Figure A. Make sure the temperature probe is in channel 1. Then, using a link cable, connect the CBL unit to the graphing calculator. 2. Turn on the CBL unit and the graphing calculator. Press the PRGM button on the calculator and choose ChemBio from the list of programs. Press ENTER on the calculator twice. 3. Choose SET UP PROBES from the MAIN MENU. Enter 1 as the number of probes. On the SELECT PROBES menu, choose TEMPERATURE. Enter 1 as the channel number. Select USE STORED from the CALIBRATION MENU. Part B: Collecting Freezing Point Data 1. Fill a 400-mL beaker half full with ice, and then 2.

3.

4.

5.

add 100 mL of water. Put 5–7 mL of water into a test tube and set up the apparatus as shown in Figure A. Do not lower the test tube of water into the ice water until you have set up the calculator for data collection. (See step 3.) From the MAIN MENU, select COLLECT DATA. On the DATA COLLECTION menu, select TIME GRAPH. Enter 15 as the time (in s) between samples and then enter 80 as the number of samples. The CBL unit will collect data for 20 min. Press ENTER; then select USE TIME SETUP to continue. Note: If you want to change the sample time or sample number you entered, select MODIFY SETUP. Enter 15 as the minimum temperature (Ymin) and 100 as the maximum temperature (Ymax). Enter 1 as the temperature increment (Yscl).

7.

8.

9.

10. 11.

of ice water and press ENTER on the calculator to begin data collecting. After lowering the test tube, add 5 spoonfuls of salt to the beaker and stir with a stirring rod. Continue to stir the ice water. During data collection, slowly stir the water in the test tube containing the temperature probe. If all the ice in the beaker melts, add additional pieces of ice to the beaker. Once crystals begin to form in the water, stop stirring and let the probe freeze in the water. After 20 minutes, the CBL will stop collecting data. If you think the lab is complete before 20 minutes, you may stop the run by pressing the button of the calculator to stop the program. See page v for sending data for graphical analysis. On the displayed graph, analyze the flat part of the curve to determine the freezing temperature of water. Save your data. Ring stand with clamp

Temperature probe Graphing calculator

Test tube with water or BHT

CBL unit Beaker with ice water

Link cable

Figure A

10




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3

Part C: Collecting Melting Point Data 1. Set up the CBL for taking data as in steps 3–5

of Part B. 2. Take the test tube of frozen water out of the ice bath and place it in the hot-water bath. Heat the test tube slowly. Allow the CBL to take data until the water has completely melted. Follow directions on page X to save your data. Part D: Collecting BHT Data

Class

CBL LABORATORY MANUAL Cleanup and Disposal 1. Dispose of the salt–ice solution following your

teacher’s directions. 2. Place the BHT test tube in the hot-water bath your teacher has prepared. 3. Clean up the lab area and wash your hands with soap or a detergent.

Data and Observations Data Table 1

Obtain a BHT test tube that your teacher has prepared for you. Repeat parts B and C using the BHT. Substance

Freezing point (°C)

Melting point (°C)

Water BHT

Analyze and Conclude 1. Observing and Inferring What is the freezing point of water? Of BHT? What evidence


do you have?

2. Collecting and Interpreting Data What is the relationship between melting point and

freezing point? Explain your answer.

3. Recognizing Cause and Effect Use the concept of molecular motion to describe why

the temperature does not change during a phase change.



11

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4. Drawing a Conclusion Look at the structures of water and of BHT. Suggest an

explanation for the differences in their melting/freezing points.

5. Thinking Critically What role did the salt play in this investigation?

Real-World Chemistry 1. How could a scientist know if he or she had

2. Why does ice float in a glass of water?


pure water or pure BHT based on the tests you just completed?

12



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4

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Boyle’s Law

S


uppose you have a basketball containing a given volume of air. If you were to sit on the ball, its volume would decrease. What happens to the particles of air inside the ball? They would be forced to occupy a smaller volume. Because the particles are more crowded, collisions among particles and between the particles and the inside surface of the ball increase. This increase in the number of collisions causes an increase in pressure inside the ball. The relationship between the volume of a gas and the pressure it exerts is known as Boyle’s law, and it can be studied in a laboratory setting.

Problem

Objectives

Materials

What is the relationship between the volume and pressure in a closed system?

• Collect data that relate pressure to volume. • Analyze laboratory data and develop a mathematical expression to show the relationship between pressure and volume. • Calculate pressure of an unknown gas.

CBL unit TI graphing calculator link cable AC adapter for CBL unit CBL-DIN adapter gas pressure sensor syringe

Safety Precautions • Always wear safety goggles and a lab apron. • Use caution when pushing on syringe. • Use caution when making electrical connections.

Pre-Lab 1. Sketch three syringes at equal temperature and

containing an equal number of gas particles. Show the plungers at three different volumes— 5 mL, 15 mL, and 20 mL. Use dots to represent the gas particles. How do the contents of the three syringes appear to be different? How does the pressure differ in the three syringes?


2. What is the definition of pressure, volume, and

temperature? 3. Read over the entire laboratory activity. Form a hypothesis as to how volume and pressure are related in a closed system. Record your hypothesis on page 14. 4. What variables are changed in this lab? What is held constant?


13

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CBL LABORATORY MANUAL Figure A DIN adapter TI calculator

CBL unit Gas pressure sensor

Syringe

AC adapter for CBL unit Link cable

2. Press the plunger of the syringe down to the 5 mL

Part A: Preparing the CBL System 1. Connect the syringe to the gas pressure sensor.

Then connect the CBL unit to both the gas pressure sensor and the graphing calculator as shown in Figure A. Make sure the gas pressure sensor probe is in channel 1. 2. Turn on the CBL unit and the graphing calculator. Press the PRGM button on the calculator and choose ChemBio from the list of programs. Press ENTER on the calculator twice. 3. Choose SET UP PROBES from the MAIN MENU. Enter 1 as the number of probes. On the SELECT PROBES menu, choose PRESSURE. Enter 1 as the channel number. Then select USE STORED from the CALIBRATION menu and select ATM for your units. You will be returned to the MAIN MENU. 4. From the MAIN MENU, select COLLECT DATA. On the DATA COLLECTION menu, select TRIGGER PROMPT. Follow the directions on the calculator to collect data.

3. 4.

5. 6.

mark. When the pressure gauge stops changing, press TRIGGER on the CBL unit. Enter 5 as the mL on the graphic calculator. From the DATA COLLECTION menu, select MORE DATA. Repeat steps 1 through 3, pressing the plunger of the syringe down to the 7.5 mL, 10.0, mL, 12.5 mL, 15.0 mL, 17.5 mL, and 20.0 mL marks. After the last set of data, select STOP AND GRAPH. Select GRAPH on your calculator to see a line graph. Press STAT and then choose EDIT. The data are now displayed. Volume will be in Column 1 and pressure will be in Column 2. Record these data in Data Table 1.

Cleanup and Disposal Disconnect the sensor from the CBL unit. Following your teacher’s directions, return all equipment to its proper place.

Hypothesis Part B: Collecting Data 1. Open the blue valve between the atmosphere and

the syringe. Set the inside ring of the syringe to the 20 mL mark and close the blue valve to the atmosphere.

14




Procedure

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Data and Observations Data Table 1 Volume (mL)

Pressure (ATM)

Constant (pv or p/v)

5.0 7.5 10.0

Analyze and Conclude 1. Collecting and Interpreting Data As the volume changes from 10 to 20 mL, what

happens to the pressure?

2. Observing and Inferring Is the relationship between volume and pressure an inverse or Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.

a direct relationship?

3. Thinking Critically Why is the graph you see a curved line, not a straight line? What

mathematical function would you have to graph to achieve a straight line?

4. Predicting Predict what the pressure of the gas in the syringe would be if the volume

was increased to 40 mL.



15

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5. Recognizing Cause and Effect Why was it necessary to keep temperature and number

of gas particles constant during this activity?

6. Error Analysis What could be done to improve the accuracy of this investigation?

Real-World Chemistry 1. Why would it be important for a scuba diver to

2. What are some common household products

that utilize Boyle’s law?


be familiar with Boyle’s law?

16



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5

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Gay-Lussac’s Law

H


ave you ever tried to bounce a cold basketball or walked outside in the cold with a helium balloon? Why is it never advisable to heat a sealed container? As you might predict, these items act in an odd manner under different temperature conditions. Why does this happen? In this lab, you will investigate the relationship between temperature and pressure, as proposed by Joseph Gay-Lussac.

Problem

Objectives

Materials

What is the relationship between the temperature and pressure of a sealed container of gas at a constant volume?

• Develop a mathematical expression to show the relationship between temperature and volume. • Determine a temperaturevolume constant. • Make calculations on unknown gases based on a determined temperature-volume constant.

CBL unit TI graphing calculator Vernier CBL pressure sensor (attached to rubber stopper assembly) Vernier temperature probe 1000-mL beakers (3) 150-mL Erlenmeyer flask ice thermal mitt hot plate

Safety Precautions • Always wear safety goggles and a lab apron. • Use caution when working around a hot plate and hot glassware. • Use caution when making electrical connections.

Pre-Lab

Procedure

1. What are temperature and pressure?

Part A: Preparing the CBL System

2. Describe these three containers in relationship to

1. Connect the CBL unit to the pressure sensor and

each other in terms of particle speed and collisions with the walls of the container. All have same amounts of the same gas in them. a. 1-L container at 25°C b. 1-L container at 150°C c. 1-L container at 300°C 3. Read over the entire lab activity. What variables will be held constant in this lab?

temperature probe, as shown in Figure A. Make sure the pressure sensor is in channel 1 and the temperature probe is in channel 2. Use the link cable to connect the CBL to the graphing calculator. 2. Turn on the CBL unit and the graphing calculator. Press the PRGM button on the calculator and choose ChemBio from the list of programs. Press ENTER on the calculator twice.



17

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3. Choose SET UP PROBES from the

Channel 2

Pressure sensor

CBL unit

4. 5.

18

1000-mL beaker

Link cable

1. Prepare three water baths: a. To prepare a boiling-water bath, pour about

3.

Erlenmeyer flask

Graphing calculator

Part B: Collecting Data

2.

Channel 1

800 mL of water into a 1000-mL beaker and place it on a hot plate on high. b. To prepare an ice-bath, pour about 700 mL of cold tap water into a second 1000-mL beaker and add ice. c. Pour about 800 mL of room-temperature water into a third 1000-mL beaker. Insert the rubber stopper assembly, connected to the pressure sensor, into the 150-mL Erlenmeyer flask, with the valve open to the atmosphere. Twist the stopper into the flask to insure a tight fit. Close the valve to the atmosphere. If the stopper pops out at any time during the experiment, you must start over. Begin with the hot water to prevent this. Carefully place the stoppered Erlenmeyer flask into the hot-water bath with the temperature probe in the beaker of water next to but not in the flask, as illustrated in Figure A. Now press ENTER on the calculator to begin monitoring pressure and temperature. After the temperature and a pressure have stabilized, press the TRIGGER button on the CBL unit. This will store the temperature and pressure in the list on the calculator. Follow the calculator directions to take more data.


Figure A 6. After the temperature and pressure of the hot

water are recorded, carefully remove the flask and place it in the room-temperature beaker with the temperature probe beside the flask in the water. Continue to monitor the CBL until it stabilizes and then press the TRIGGER button on the CBL unit. 7. Repeat steps 3–6 for the beaker with the ice water. Ask your teacher whether you should take more data points. After three data points, press END to stop collecting data. 8. Select GRAPH on your calculator. Press STAT and then choose EDIT. The data are now displayed. Record these data in Data Table 1.

Cleanup and Disposal 1. Turn off your hot plate and unplug it. 2. Turn off the calculator and the CBL unit, and

then unplug them. 3. Return the CBL unit and the probes to the appropriate location. 4. Clean up and organize your lab area.



MAIN MENU. Enter 2 as the number of probes. On the SELECT PROBE menu, choose PRESSURE. Enter 1 as the channel number. Then select USE STORED from the CALIBRATION MENU and select ATM for your units. 4. On the SELECT PROBE menu, next choose TEMPERATURE. Enter 2 as the channel number. Then select USE STORED from the CALIBRATION MENU and select COLLECT DATA from the MAIN MENU. On the DATA COLLECTION MENU, select TRIGGER prompt. Follow the directions on the calculator to collect data.

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Data and Observations Data Table 1 Trial

Pressure (atm)

Temperature (°C)

Temperature (K)

Constant (P T or P/T)

1 2 3

Analyze and Conclude 1. Measuring and Using Numbers Convert the Celsius temperatures to kelvin. Record

these temperatures in Data Table 1. 2. Observing and Inferring Is the relationship between temperature and pressure a direct or an inverse relationship? Explain your answer.

3. Measuring and Using Numbers Determine a constant for this relationship. Is it P T


or P/T?

4. Predicting What would the pressure of the gas in the container be if the temperature

was 33°C?

5. Observing and Inferring Why was it necessary to keep the volume constant during this

experiment?

Real-World Chemistry 1. Why is it necessary for a hot-air balloonist,

who is traveling around the world, to be familiar with Gay-Lussac’s law?


2. During which season should motorists keep

more air in their tires—winter or summer?


19

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Determining Molar Mass Using Freezing Point Depression


T


he freezing point depression of a solution is a colligative property of the solution. A temperature versus time graph can be used to determine the freezing point of a particular substance. A plateau occurs on the graph at the freezing point because no change in average kinetic energy of the system takes place as the phase change occurs. This allows the freezing point of a pure substance to be compared with that of a solution. From this comparison, it is possible to determine the molecular mass of an unknown substance. In this lab, an organic solute will be used to determine a freezing point depression constant for the food additive BHT (butylated hydroxytolune). Using this information, you will determine the molecular mass of an unknown substance.

Problem

Objectives

Materials

What is the molecular mass of an unknown substance?

• Describe the process of melting and freezing. • Collect data to determine the Kf for BHT. • Compare melting point graphs to determine the molecular mass of the unknown substance. • Analyze the results and complete an error analysis.

CBL unit TI graphing calculator link cable temperature probe adapter cable BHT (butylated hydroxytoluene C15H24O) PDB (paradichlorobenzene)

unknown substance 400-mL beaker 1-mL graduated cylinder test tubes (2–3) hot plate ring stand universal clamp laboratory balance copper wire stirrer scoop

Safety Precautions • Always wear safety goggles and a lab apron. • Use caution when working with the hot plate. • Some of these chemicals are flammable and may have toxic vapors; you may want to work in a fume hood. • Dispose of materials as your teacher instructs.

Pre-Lab 1. Sketch the cooling curve for water and identify its

key features. 2. What is molality?


3. If 2.8 grams of NaCl is added to 50.0 grams of

water, at what temperature would you expect the solution to freeze? (Density of water 1.0 g/cm3)


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6


4. What is the molar mass of BHT? What is the

6. Press ENTER and then select USE TIME SETUP

molar mass of PDB? 5. Read over the entire laboratory activity. Describe the process you will use to melt the pure solids.


to continue. Note: If you wish to change the sampling time or number of samples, select MODIFY SETUP. 7. Enter 15 as the minimum temperature (Ymin), 100 as the maximum temperature (Ymax), and 1 as the temperature increment (Yscl).

1. Using the adapter cable, connect the CBL unit to

Part B: Collecting Data

Procedure

the temperature probe, as shown in Figure A. Make sure the temperature probe is in channel 1. Then, using a link cable, connect the CBL unit to the graphing calculator

1. Add approximately 300 mL of water to the

2. Adapter cable CBL unit Temperature probe

TI graphing calculator

3.

Test tube

4. 5. Figure A

Link cable

6. 2. Turn on the CBL unit and the graphing calculator.

Press the PRGM button on the calculator and choose ChemBio from the list of programs. Press ENTER on the calculator twice. 3. Choose SET UP PROBES from the MAIN MENU. Enter 1 as the number of probes. On the SELECT PROBES menu, choose TEMPERATURE. Enter 1 as the channel number. 4. Select USE STORED from the CALIBRATION MENU. 5. From the MAIN MENU, select COLLECT DATA. Select TIME GRAPH from the DATA COLLECTION MENU. Enter 15 as the time (in s) between samples and enter 60 as the number of samples. The CBL unit will collect data for 15 minutes. 22


7.

400-mL beaker and place the beaker on the hot plate. Turn on the hot plate and heat the water to approximately 90°C. Using a laboratory balance, measure the mass of an empty test tube and record the value in Data Table 1. Add about 8.0 g of BHT to the test tube. Measure the total mass of the test tube and BHT and record the measurement. Use the clamp to suspend the test tube in the hot water bath. After the BHT has melted completely, reposition the clamp so the test tube is not over the hot water bath or the hot plate. Place the temperature probe into the BHT mixture and press ENTER on the calculator to begin collecting data. To maintain even cooling, stir the BHT continuously using the copper wire stirrer. After the data collection is complete, make a graph by transferring the data to a computer using the directions from page v. Using the same BHT sample, add about 1.0 g of para-dichlorobenzene (PDB) to the test tube. Record the mass in Data Table 1. Repeat steps 3–5 above. Be sure to stir the solution once it has all melted. Repeat steps 1–6 using a clean test tube, about 8.0 g of BHT, and about 1.0 g of the unknown. Be sure the two substances are well mixed during the melting phase.

Cleanup and Disposal 1. Dispose of or store the chemical as directed by

your teacher. 2. Rinse the probes with distilled water. Dispose of the rinse water in an appropriate container. 3. Clean up lab tables and wash your hands with soap or detergent before leaving the lab. CBL Laboratory Manual


LAB

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6

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Data and Observations Data Table 1 Substance

Mass (g)

Empty test tube 1 Test tube 1 BHT Test tube 1 BHT PDB BHT PDB Empty test tube 2 Test tube 2 BHT Test tube 2 BHT unknown BHT Unknown

Calculate the masses of the BHT, PDB, and unknown substance.


Analyze and Conclude 1. Observing and Inferring Using the graphs, determine the melting point for each of the

following: pure BHT; BHT PDB; BHT unknown.

2. Collecting and Interpreting Data a. What is the difference in freezing point between pure BHT and the solution of BHT

and PDB?

b. What is the difference in freezing point between pure BHT and the solution of BHT

and the unknown?

3. Measuring and Using Numbers Calculate the molality of the solution of BHT and

PDB (in mol solute/kg solvent).



23

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4. Measuring and Using Numbers Calculate the freezing point depression constant Kf for

BHT. (Tf Kf m)

5. Thinking Critically Why was a solvent with a large Kf value used in this activity?

6. Error Analysis Calculate the molecular mass of the unknown and compare it to the

Real-World Chemistry 1. How does antifreeze help cars in both the

winter and the summer?

24


2. Why do road crews in snowy climates keep a

supply of CaCl2 on hand? Explain why CaCl2 works better than NaCl.



actual molecular mass provided by your teacher. Calculate the percent error of the experimentally determined molecular mass.

Name

LAB

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7

Class


Calorimetry

H

eat is energy that is being transferred from a hot object to a colder object. If you know how much heat a substance can absorb and hold, the amount of energy transferred between two substances can be determined. On a hot, sunny day, heat from the Sun might go into a cool glass of lemonade and melt the ice. On a cold winter day, heat may leave a hot cup of coffee and warm up the air around it. In this lab, specific heat is used to follow the flow of energy and to determine the temperature of a Bunsen burner flame.

Problem

Objectives

Materials

What is the temperature of a Bunsen burner flame?

• Diagram a flowchart that depicts the flow of energy in this experiment. • Calculate the amount of energy transferred between two systems.

CBL unit TI graphing calculator link cable AC adapter temperature probe nickel coin

100-mL graduated cylinder Bunsen burner large plastic-foam cup tongs matches


Safety Precautions • Always wear safety goggles and a lab apron. • Be careful when working with an open flame, and tie back long hair. • Once the nickel is heated, the tongs will be hot. Do not touch them.

Pre-Lab

Procedure

1. What is the difference between heat and


2. 3.

4.

5.

temperature? What is meant by specific heat? What is the specific heat of water? Of nickel? What equation can be used to calculate the amount of heat transferred between two substances? How much energy (in cal) would it take to raise the temperature of 5.00 g of water from 20°C to 30°C? Read the entire laboratory activity. Sketch a diagram to show the flow of heat.


1. Connect the CBL unit to the temperature probe,

as shown in Figure A. Make sure the temperature probe is in channel 1. Then, using a link cable, connect the CBL unit to the graphing calculator. 2. Turn on the CBL unit and the graphing calculator. Press the PRGM button on the calculator and choose ChemBio from the list of programs. Press ENTER on the calculator twice. 3. Choose SET UP PROBES from the MAIN MENU. Enter 1 as the number of probes. On the SELECT PROBES menu, choose TEMPERATURE. Enter 1 as the channel number.


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CBL LABORATORY MANUAL 4. Using tongs, hold the nickel in the Bunsen

Figure A TI graphing calculator

CBL unit

Temperature probe

5. 6.

7. AC adapter Link cable

4. From the MAIN MENU, select COLLECT

DATA. On the DATA COLLECTION menu, select MONITOR. Do NOT press ENTER until you are ready to monitor the temperature.

8.

burner flame until it glows red. This should take 3–5 min. If the nickel has been used previously, it may not glow red. Now press ENTER on the graphing calculator to begin monitoring temperature. Place the temperature probe in the water in the cup. Read the temperature and record the initial temperature of the water in Data Table 1. Leave the temperature probe in the water. Quickly, but carefully, take the nickel out of the flame and drop it in the water. CAUTION: Do not allow the hot nickel to touch the sides of the cup. Carefully stir the water with the temperature probe and monitor the temperature. Record in Data Table 1 the highest temperature that the water reaches. Pour out the water and the nickel into the sink. Repeat steps 1–7 using 60 mL of water and again using 80 mL of water.

Part B: Collecting Data water and pour it into the cup. 2. Determine the mass of your nickel and record it in Data Table 1. 3. Turn on the gas and light the Bunsen burner. Create as hot a flame as possible. CAUTION: Be careful when working with an open flame, and tie back long hair.

Cleanup and Disposal 1. Make sure the gas to the Bunsen burner is shut

off completely. 2. Turn off and unplug the CBL unit. 3. Return all equipment to its proper place. Clean up the lab area.


Trial

26

Mass of nickel (g)

Volume of water (mL)


Initial temperature of water (°C)

Final temperature of water (°C)

Change in temperature of water, or T (°C)



1. Using a graduated cylinder, measure 40 mL of tap

Name

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Analyze and Conclude 1. Using Numbers For each trial, determine the change in the water temperature, T, and

record it in Data Table 1. (T Tfinal Tinitial) 2. Observing and Inferring How much energy (in cal) was absorbed by the water in each trial? How do your three results compare? (Specific heat of water is 1.00 cal/g°C.) Assume the density of water is 1.00 g/mL.

3. Thinking Critically How much heat did the nickel lose in each trial?

4. Drawing a Conclusion Using the information from questions 2 and 3, what is the

temperature of the Bunsen burner flame?

5. Communicating Post your data on the board and compare it with the class data. What is Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.

the average temperature calculated by your class for the Bunsen burner flame?

6. Error Analysis Compare your Bunsen burner flame temperature with the actual

temperature that your teacher gives you. How close were you? What might have been some sources of error in this lab? What assumptions were made that may have caused errors in your numbers?

Real-World Chemistry 1. Why might it be effective for homeowners to

use a water-heater blanket around the water heaters in their homes?


2. How is a thermos bottle able to keep hot

liquids hot and cold liquids cold?


27

Name

LAB

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8

Class


Hess’s Law

H

ess’s law states that the heat gained or released in a chemical reaction is the sum of the heat gained or released during the individual steps of that reaction. In this lab, you will determine the molar enthalpy of reaction (Hrxn) for three chemical reactions. Then, you will use Hess’s law to verify the experimental value obtained for one of these reactions.

Problem

Objectives

Materials

How can the enthalpy changes for two chemical reactions be used to obtain the enthalpy change for the reaction of ammonia with hydrochloric acid? NH3(aq) HCl(aq) 0 NH4Cl(aq)

• Measure the heat absorbed or released in three chemical reactions. • Determine the molar enthalpy of each reaction. • Apply Hess’s law to verify one of the experimental results.

CBL unit TI graphing calculator link cable AC adapter temperature probe 2.0M HCl 2.0M NH4Cl

Is this an exothermic or endothermic reaction?

2.0M NaOH 2.0M NH3(NH4OH) 100-mL graduated cylinders (2) thermometers (2) large plastic-foam cup glass stirring rod


Safety Precautions • Always wear safety goggles and a lab apron. • Use caution when working with acids and bases. • The reaction of ammonium chloride and sodium hydroxide releases ammonia; the reaction should be performed in an operating fume hood.

Pre-Lab 1. Read the entire laboratory activity. Describe

Hess’s law in your own words. 2. Describe how specific heat is used in calorimetry. 3. Describe in your own words what is meant by H.

Procedure Part A: Preparing the CBL System 1. Connect the CBL unit to the temperature probe,

as shown in Figure A. Plug the adapter cable into channel 1 of the CBL unit and then plug a temperature probe into the adapter cable. Make sure the temperature probe is in channel 1.


Then, using a link cable, connect the CBL unit to the graphing calculator. 2. Turn on the CBL unit and the graphing calculator. Press the PRGM button on the calculator and choose ChemBio from the list of programs. Press ENTER on the calculator twice. 3. Choose SET UP PROBES from the MAIN MENU. Enter 1 as the number of probes. On the SELECT PROBES menu, choose TEMPERATURE. Enter 1 as the channel number. Select USE STORED from the CALIBRATION MENU.


29

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8

CBL LABORATORY MANUAL 6. Pour the HCl solution into the cup and insert

Figure A Adapter cable CBL unit

TI graphing calculator

7.

Temperature probe

8.

Plastic-foam cup Link cable

9.

Part B: Collecting Data 1. For reaction 1, measure 50 mL of 2.0M HCl in

2.

3.

4.

5.

30

a 100-mL graduated cylinder. Measure 50 mL of 2.0M NaOH in a second 100-mL graduated cylinder. From the MAIN MENU, select COLLECT DATA. On the DATA COLLECTION MENU, select TIME GRAPH. Enter 30 as the time (in s) between samples and then enter 3 as the number of samples. The CBL unit will collect data for 4 min. Press ENTER, then select USE TIME SETUP to continue. Note: If you want to change the sample time or sample number you entered, select MODIFY SETUP. Enter 0 as the minimum temperature (Ymin) and enter 50 as the maximum temperature (Ymax). Enter 1 as the temperature increment (Yscl). Do not hit ENTER to begin collecting data yet. Using two thermometers, measure the initial temperatures of the two solutions and record them in Data Table 1. If the two initial temperatures are less than 0.2°C apart, average the two temperatures and use the average as the initial temperature.


10.

11.

the temperature probe from the CBL unit. Press ENTER to begin taking data. Then, cautiously pour the NaOH solution into the cup while stirring with a glass stirring rod. Have the CBL unit take data every 30 s for 4 min as the reaction continues. Continue to stir the solution slowly and monitor the CBL unit and calculator. If your calculator has a sleep function, be sure to press a number button occasionally to keep it from shutting off. When the CBL unit has stopped taking data, turn the CBL unit off and download the data from the graphing calculator to the computer, following the instructions in Appendix A. Save your data. Using distilled water, thoroughly rinse the thermometers and wash out the graduated cylinders. Repeat steps 1–8 for reaction 2 using 50 mL of 2.0M NH4Cl with 50 mL of 2.0M NaOH. Thoroughly rinse the thermometers and graduated cylinders again with distilled water and repeat steps 1–8 for reaction 3 using 50 mL of 2.0M NH3 with 50 mL of 2.0M HCl. Download the data from the calculator to a computer after each trial and save the data.

Cleanup and Disposal 1. Wash all solutions down the drain with plenty 2. 3. 4. 5.

of water. Rinse the graduated cylinders. Rinse the probes with distilled water. Turn off the CBL unit and unplug it. Return all equipment to its proper place, clean up the lab area, and wash your hands with soap or detergent.



LAB

Class

Name

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LAB

8

Class


Data and Observations Data Table 1 Reaction

Initial temperature before mixing (Tinitial)

Temperature directly after mixing (Tmix), derived from graph

1 2 3

Analyze and Conclude 1. Making and Using Graphs Make a graph of the data from each of the three trials. Plot

time (s) on the x-axis and temperature (°C) on the y-axis. 2. Acquiring and Analyzing Information Draw a best fit line through your data. The line

should intercept the y-axis. The point at which the line intercepts the y-axis is the temperature directly after mixing (Tmix). Record Tmix in Data Table 1. 3. Measuring and Using Numbers Assume the density of the mixed solutions is


1.03 g/mL. Assume that the specific heat of the solutions is the same as the specific heat of water, 4.18 J/g°C. Using the following equations, determine the enthalpy change for each reaction. a. Tsolution Tmix Tinitial b. qreaction (grams of solution specific heat of solution Tsolution)

4. Measuring and Using Numbers What is the molar enthalpy for each of the three

reactions in kJ/mol?



31

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5. Observing and Inferring Rearrange the equations for reactions 1 and 2 to obtain the

equation for reaction 3. Determine the change in enthalpy for reaction 3. Compare this result with the enthalpy change you obtained by direct measurement.

6. Classifying Classify reactions 1, 2, and 3 as exothermic or endothermic. 7. Error Analysis Every measurement involves a certain amount of error. Which of the

two values for H for reaction 3 is likely to have the greater error? What is the largest source of error in this lab?

Real-World Chemistry


Explain how cold packs and hot packs work.

32



Name

LAB

Date

9

Class


Determine the Molar Mass of an Unknown Acid


A

ccording to the Arrhenius definition of acids and bases, acids are substances that produce hydrogen ions (H) in solution, and bases are substances that produce hydroxide ions (OH) in solution. When an acid and a base combine, the hydrogen ions from the acid react with the hydroxide ions from the base to form water—a neutralization reaction.


In a neutralization reaction, moles of H ions equal moles of OH ions. This relationship is the basis for the procedure called titration, which you will use to standardize a base solution. Standardizing a base means determining its molar concentration. You will then use your standardized base to determine the molar mass of an acid. To determine when the moles of H equal the moles of OH, you will monitor the pH of an acid solution as a solution of base is added slowly. The pH will rise suddenly when the concentrations of the two ions are equal (the equivalence point).

Problem

Objectives

Materials

What is the molar mass of an unknown acid?

• Standardize a sodium hydroxide solution. • Determine the molar mass of an unknown acid using titration data.

CBL unit pH probe TI graphing calculator link cable potassium hydrogen phthalate (KHP) NaOH solution unknown acid phenolphthalein solution 250-mL beakers (2)

250-mL Erlenmeyer flask 50-mL burette wash bottle with distilled water funnel ring stand weighing paper or dish microspatula or scoop balance, sensitive burette clamp utility clamp

Safety Precautions • Always wear safety goggles and a lab apron. • Use caution when working with acids and bases. • Wipe up any water spills to avoid slipping.



33

Name

Date

LAB

9

Pre-Lab

Class

CBL LABORATORY MANUAL Figure A pH probe

1. Define the following terms: (a) acid, (b) base,

(c) neutralize, (d) titration, and (e) pH. 2. Write a balanced equation for the dissociation of (a) HCl, (b) H2SO4, (c) NaOH, (d) Mg(OH)2 3. Read the entire laboratory activity. Write the balanced chemical equation for each of the following: a. hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) b. sulfuric acid (H2SO4) reacts with sodium hydroxide (NaOH)

Burette

Graphing calculator

Burette clamp

CBL unit

Ring stand

Erlenmeyer flask

Procedure 5. Using a weighing dish, measure 0.4–0.6 g of

1. Connect the CBL unit to the pH probe. Make sure

the pH probe is in channel 1. Then, using a link cable, connect the CBL to the graphing calculator. 2. Turn on the CBL unit and the graphing calculator. Press the PRGM button on the calculator and choose ChemBio from the list of programs. Press ENTER on the calculator twice. 3. Choose SET UP PROBES from the MAIN MENU. Enter 1 as the number of probes. On the SELECT PROBES menu, choose pH. Enter 1 as the channel number. Select USE STORED from the CALIBRATION MENU.

6.

7.

8.

Part B: Standardizing NaOH 1. Set up the burette, burette clamp, 250-mL

Erlenmeyer flask, the CBL, and pH probe for titration as shown in Figure A. 2. Pour about 70 mL of NaOH solution into a 250-mL beaker. 3. Using a funnel, carefully fill the burette to the zero line with the NaOH solution. 4. To eliminate any air in the burette tip, allow a little of the NaOH solution to run through the tip into a 250-mL waste beaker. Then refill the burette to the zero line.

34


9.

10.

potassium hydrogen phthalate (KHP). Record the mass of KHP in Data Table 1. Transfer the KHP to a 250-mL Erlenmeyer flask. With a wash bottle filled with distilled water, rinse any residue from the weighing dish into the flask. Add about 40 mL of distilled water to the Erlenmeyer flask and swirl until the solid KHP is completely dissolved. Then add 3 drops of phenolphthalein to the acid in the flask. From the MAIN MENU, select COLLECT DATA. On the DATA COLLECTION MENU, select TRIGGER PROMPT. Follow the directions on the calculator to collect data. Insert the pH probe into the KHP solution. When the pH meter is stable, press TRIGGER on the CBL unit. The calculator will read VALUE? Enter 0 for the volume of NaOH that has been added. This will give you the initial pH value. From the DATA COLLECTION MENU, select MORE DATA. Add 1 mL of NaOH from the burette to the Erlenmeyer flask while swirling. After the pH has stabilized once more, press TRIGGER on the CBL unit and enter 1 for the number of mL of NaOH added. Always enter the total volume of NaOH that has been added to the Erlenmeyer flask.




Name

Date

LAB

9


11. Continue to add the NaOH solution 1 mL at a

12.

13. 14.


15.

Class

time and take pH readings after each addition, until the pH begins to change. Then, add the NaOH solution by 0.5 mL and finally, by 1-drop increments until the pH rises quickly. This is the equivalence point. Record in Data Table 1 the total volume of NaOH used at this point. After you have reached the equivalence point, add a few more mL of NaOH, making pH measurements after every 1 mL addition. If no more change occurs, the titration is complete. Note the color of the solution in the beaker. Download your data to the computer following the procedure in Appendix A. Rinse the 250-mL Erlenmeyer flask. Repeat steps 2–13 as many times as your teacher directs. Use your data to calculate the concentration of the NaOH. Use the class average of this concentration for Part C of this activity.

Part C: Titrating an Unknown Acid 1. Fill the burette to the zero line with your stan-

dardized NaOH solution. 2. Using a clean weighing dish, measure 0.3–0.4 g of the unknown acid into a 250-mL Erlenmeyer flask. Rinse any residue into the flask. Record the mass in Data Table 2. 3. Dissolve the unknown acid in about 40 mL of distilled water. Swirl to completely dissolve the acid. 4. Titrate the unknown acid following the procedure described in steps 2–13 of Part B. Record the volume of NaOH solution in Data Table 2.

Cleanup and Disposal 1. Rinse the beakers and Erlenmeyer flask with

plenty of water. 2. If not being used again, empty the burettes and clean them according to your teacher’s directions. 3. Disconnect the pH sensor and TI graphing calculator from the CBL unit. Following your teacher’s directions, return all equipment to its proper place.

Data and Observations Data Table 1: Standardization of Base (Molar Mass of KHP 204.2 g/mol) Mass of KHP

Mol KHP

Volume of NaOH (L)

Mol NaOH

Concentration of NaOH (mol/L)

Data Table 2: Molar Mass of Unknown Acid Volume of NaOH (L)

Concentration of NaOH (mol/L)


Mol NaOH

Mol of unknown acid

Mass of unknown acid (g)

Molar mass of unknown acid (g/mol)


35

Name

Date

LAB

9

Class


Analyze and Conclude 1. Measuring and Using Numbers KHP has one ionizable H ion per mole of KHP.

What is the ratio of moles of NaOH to moles of KHP in this reaction? 2. Measuring and Using Numbers Determine the concentration of the NaOH solution and

record it in the appropriate space in Data Table 1.

3. Acquiring and Analyzing Information In Part C, how many moles of NaOH did it

take to neutralize the unknown acid? Your teacher will tell you how many ionizable hydrogen atoms are in your unknown acid. What is the molar ratio of acid to base for this reaction? What is the molar mass of the unknown acid?

4. Error Analysis Your teacher will give you the molar mass of the unknown acid.

Determine your percent error for this experiment.

concentration of the NaOH solution compare to the actual concentration? a. The mass of the acid was measured correctly, but some of it was spilled on the counter when transferring it to the Erlenmeyer flask.

b. Although not noticed, some of the NaOH was spilled on the counter, instead of going

into the flask with the acid.

Real-World Chemistry 1. Why is it important to monitor the pH levels of

lakes, ponds, rivers, and streams?

36


2. Name some common antacids and describe

what ingredients make them work. How do they help upset stomachs?



5. Error Analysis If the following errors occurred, how would your calculated

Name

LAB

Date

10

Class


Reaction Potentials of Metals

Use after Section 21.1

A

voltaic cell is a device that converts chemical energy to electrical energy. This is done by harnessing the electron flow generated by a spontaneous redox reaction. A voltaic cell consists of two half-cells connected by a conducting wire and a salt bridge. One half-cell, called the anode, contains a metal in a solution of its ions and is the site of oxidation. The other half-cell, called the cathode, contains a different metal in a solution of its ions and is the site of reduction. The conducting wire carries the flow of electrons. The salt bridge allows ions to flow from one side to the other so the redox reaction can continue.


In this lab, a voltage probe is used to measure the flow of electrons through voltaic cells made of different metals. The metal attached to the positive lead of the voltage probe is the cathode and has a higher reduction potential. The metal attached to the negative lead is the anode and has a lower reduction potential. The reduction potentials of five metals will be compared, resulting in a chart for understanding the potentials of metals.

Problem

Objectives

Materials

Rank a series of different metals from lowest reduction potential to highest reduction potential. How can the cell potential for two half-reactions be calculated?

• Measure the amount of current flowing between two half-cells of a reaction. • Predict the cell potentials of a two-metal system. • Analyze the data in order to rank the metals from a high reduction potential to low reduction potential.

CBL unit TI graphing calculator voltage probe link cable adapter cable 1M solution of each of the following: sodium nitrate (NaNO3) copper sulfate (CuSO4) zinc sulfate (ZnSO4) lead nitrate (Pb(NO3)2) silver nitrate (AgNO3)

iron sulfate (FeSO4) 1 1-cm pieces of the following metals: copper zinc lead silver iron large watch glass forceps scissors sandpaper filter paper

Safety Precautions • Always wear safety goggles and a lab apron. • Use caution with sharp edges of metals. • AgNO3, CuSO4, Pb(NO3)2, and FeSO4 are toxic by ingestion; ZnSO4 and Pb(NO3)2 may cause skin and eye irritation; AgNO3 will stain skin and clothes. • Use forceps to handle the metals. CBL Laboratory Manual


37

Name

Date

LAB

10

Pre-Lab

Class

CBL LABORATORY MANUAL Cut along dotted lines

Figure A

1. Read over the entire laboratory activity. Define 2. 3. 4. 5.

reduction and oxidation. Write the half-reaction for (a) the oxidation of zinc; (b) the reduction of copper. What happens at the anode? What happens at the cathode? In which direction do electrons flow in a voltaic cell? Review the equation to calculate the potential of a voltaic cell.

Pb

Zn

Ag NaNO3 solution

Procedure Cu


Fe

1. Connect the CBL unit to the voltage probe. Plug

Part B: Data Collecting 1. Obtain a 1 1-cm piece of each of the following

metals: copper, zinc, lead, silver, and iron. Also obtain dropper bottles with 1M solutions of copper sulfate (CuSO4), zinc sulfate (ZnSO4), lead nitrate (Pb(NO3)2), silver nitrate (AgNO3), and iron sulfate (FeSO4) 2. Set up the equipment for the investigation. Draw dashed lines on the filter paper, as indicated in Figure A. Cut out the triangular areas between the dashed lines and place the filter paper on top of the watch glass. 38


Filter paper

3. Label the ends of the filter paper with the metal 4.

5.

6.

7.

strips to be tested (See Figure A). Place several drops of NaNO3 solution in the middle of the paper with trails of this NaNO3 solution leading out to each end of the paper. If the NaNO3 center and trails begin to dry out, reapply the NaNO3 solution throughout the activity. Next, place 3 drops of the metal ion solutions on the corresponding areas of the filter paper (indicated by the name of the metal). Using tongs, place the corresponding metal piece on top of the solution. Always keep the top of the metal dry. Note: If the metal has oxidized, shine it with sandpaper first. Using copper as a reference metal, compare the potential of the other four metals with that of copper. To do this, place the positive lead of the voltage probe on copper and the negative lead on the metal being tested. If the voltage reads negatively, reverse the leads. Wait about 5 s and record the voltage of each of the metals compared with copper in Data Table 1. Test the following combinations: Cu and Zn, Cu and Pb, Cu and Ag, and Cu and Fe.



the adapter cable in channel 1 and then plug the voltage probe into the adapter cable. Using a link cable, connect the CBL unit to the graphing calculator. 2. Turn on the CBL unit and the graphing calculator. Press the PRGM button on the calculator and choose ChemBio from the list of programs. Press ENTER on the calculator twice. 3. Choose SET UP PROBES from the MAIN MENU. Enter 1 as the number of probes. On the SELECT PROBE MENU, choose VOLTAGE. Enter 1 as the channel number. Select COLLECT DATA from the MAIN MENU. 4. From the DATA COLLECTION menu, select MONITOR INPUT. The voltage reading is now displayed on the screen. No readings will be stored in the MONITOR INPUT mode.

Name

Date

LAB

10

Class


8. Because copper was the reference metal, assign

it an arbitrary reduction potential of zero. Rank the metals in order of lowest reduction potential (most negative) to highest reduction potential (most positive) in Data Table 2. If the test metal was connected to the negative lead, then the voltage should be listed above copper and given a negative value. If the test metal was connected to the positive lead, then the voltage should be listed below copper and assigned a positive value. 9. Before experimenting further, predict the potential for the combinations given in Data Table 3. Use the information from Data Table 2 to make your predictions. Determine the actual potentials of these combinations of metals. Remember to keep the voltage positive and keep the NaNO3 moist.

10. Test the following combinations: Zn and Pb, Zn

and Ag, Zn and Fe, Pb and Ag, Pb and Fe, and Ag and Fe.

Cleanup and Disposal 1. Dispose of silver and lead products in waste

containers designated by your teacher. 2. Place all metal pieces in a solid-waste container. 3. Throw away filter paper and clean up the lab area. Wash your hands before leaving the lab. 4. Disconnect the sensor from the CBL unit. Turn off the CBL unit and graphing calculator, unplug them, and return all equipment to its proper place.



Metals used

Data Table 2

Voltage Metal

Reduction potential (lowest to highest)

Cu/Zn Cu/Pb Cu/Ag Cu/Fe

Data Table 3 Metal

Predicted potential

Measured potential

Percent error

Zn/Pb Zn/Ag Zn/Fe Pb/Ag Pb/Fe Ag/Fe



39

Name

Date

LAB

10

Class


Analyze and Conclude 1. Collecting and Interpreting Data Which metal in this experiment loses electrons most

readily? Which element gains electrons most readily?

2. Observing and Inferring How do your answers in question 1 help explain the data that

were recorded during this lab?

3. Formulating Models Sketch a diagram of the flow of electrons for one of the voltaic cells


made in the lab. Be sure to label the electrons, reduction, oxidation, cathode, and anode.

4. Thinking Critically What is the function of the NaNO3-soaked filter paper?

5. Error Analysis What may have caused any errors found in this lab?

Real-World Chemistry 1. How do lead storage batteries produce an

electric current?

40


2. Look up a reference table of reduction poten-

tials. Why might they differ from your values?


CREDITS Art Credits


Navta Associates: 2, 14, 18, 22, 26, 30; MacArt Design: 6, 10, 18, 34, 38



41

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