Glencoe chemistry CBL lab manual 0078245303

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 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 Quantitative and Qualitative Observations Conductivity Melting and Freezing Points Boyle’s Law 13 Gay-Lussac’s Law 17 Determining Molar Mass Using Freezing Point Depression 21 Calorimetry 25 Hess’s Law 29 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 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 Chemistry: Matter and Change CBL Laboratory Manual Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Organization of Activities CBL LABORATORY MANUAL Sending Data to Graphical Analysis If using the TI-83 graphing calculator: On the TI calculator, press 2nd Link, then select 4:List… from the SEND menu 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 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: 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 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 Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc 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 CBL Laboratory Manual Chemistry: Matter and Change v CBL LABORATORY MANUAL 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 Study your lab activity before you come to the lab If you are in doubt about any procedures, ask your teacher for help 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 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 Long hair should be tied back to reduce the possibility of it catching fire 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 Wear shoes that cover the feet at all times Bare feet or sandals are not permitted in the lab 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 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 so Use test tubes, paper, or beakers to obtain your chemicals vi Chemistry: Matter and Change 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 CBL Laboratory Manual Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc 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 CBL Laboratory Manual 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 Chemistry: Matter and Change vii Name LAB Date Class CBL LABORATORY MANUAL Use with Section 1.3 Quantitative and Qualitative Observations R Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc 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 ϫ 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 What is the difference between observations and interpretations? Give three examples of qualitative observations and three examples of quantitative observations CBL Laboratory Manual What are some tools that scientists use to enhance their observational techniques? Chemistry: Matter and Change • Chapter 1 Name Date CBL LABORATORY MANUAL Using the 100-mL graduated cylinder, obtain Procedure Part A: Preparing the CBL System Connect the CBL unit to the temperature probe, as shown in Figure A Make sure the temperature probe is in channel Then, using a link cable, connect the CBL unit to the graphing calculator Figure A TI graphing calculator CBL unit Temperature probe AC adapter Link cable 10 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 Choose SET UP PROBES from the MAIN MENU Enter as the number of probes On the SELECT PROBES menu, choose TEMPERATURE Enter as the channel number From the MAIN MENU, select COLLECT DATA On the DATA COLLECTION menu, select TRIGGER/PROMPT Part B: Collecting Data Obtain a ϫ 2-in square of aluminum Place a small scoop of copper(II) chloride onto a piece of weighing paper Make as many observations of the aluminum and the copper(II) chloride as possible Record your observations in Data Table Chemistry: Matter and Change • Chapter 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 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 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 Disconnect the temperature probe from the CBL unit After emptying the beaker, clean and rinse the beaker Rinse the probe with distilled water and carefully wipe it dry Return all equipment to its proper place Clean up the lab area and wash your hands with soap or detergent before leaving the lab CBL Laboratory Manual Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc LAB Class Name Date LAB Class CBL LABORATORY MANUAL Analyze and Conclude Using Numbers For each trial, determine the change in the water temperature, ⌬T, and record it in Data Table (⌬T ϭ Tfinal Ϫ Tinitial) Observing and Inferring How much energy (in cal) was absorbed by the water in each trial? How your three results compare? (Specific heat of water is 1.00 cal/gи°C.) Assume the density of water is 1.00 g/mL Thinking Critically How much heat did the nickel lose in each trial? Drawing a Conclusion Using the information from questions and 3, what is the temperature of the Bunsen burner flame? 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? 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 Why might it be effective for homeowners to use a water-heater blanket around the water heaters in their homes? CBL Laboratory Manual How is a thermos bottle able to keep hot liquids hot and cold liquids cold? Chemistry: Matter and Change • Chapter 16 27 Name LAB Date Class CBL LABORATORY MANUAL Use with Section 16.3 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) ϩ HCl(aq) 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 Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc 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 Read the entire laboratory activity Describe Hess’s law in your own words Describe how specific heat is used in calorimetry Describe in your own words what is meant by ⌬H Procedure Part A: Preparing the CBL System Connect the CBL unit to the temperature probe, as shown in Figure A Plug the adapter cable into channel of the CBL unit and then plug a temperature probe into the adapter cable Make sure the temperature probe is in channel CBL Laboratory Manual Then, using a link cable, connect the CBL unit to the graphing calculator 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 Choose SET UP PROBES from the MAIN MENU Enter as the number of probes On the SELECT PROBES menu, choose TEMPERATURE Enter as the channel number Select USE STORED from the CALIBRATION MENU Chemistry: Matter and Change • Chapter 16 29 Name Date CBL LABORATORY MANUAL Pour the HCl solution into the cup and insert Figure A Adapter cable CBL unit TI graphing calculator Temperature probe Plastic-foam cup Link cable Part B: Collecting Data For reaction 1, measure 50 mL of 2.0M HCl in 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 as the number of samples The CBL unit will collect data for 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 as the minimum temperature (Ymin) and enter 50 as the maximum temperature (Ymax) Enter 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 If the two initial temperatures are less than 0.2°C apart, average the two temperatures and use the average as the initial temperature Chemistry: Matter and Change • Chapter 16 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 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 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 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 Wash all solutions down the drain with plenty 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 CBL Laboratory Manual Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc LAB Class Name Date LAB Class CBL LABORATORY MANUAL Data and Observations Data Table Reaction Initial temperature before mixing (Tinitial) Temperature directly after mixing (Tmix), derived from graph Analyze and Conclude 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 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 Measuring and Using Numbers Assume the density of the mixed solutions is Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc 1.03 g/mL Assume that the specific heat of the solutions is the same as the specific heat of water, 4.18 J/gи°C Using the following equations, determine the enthalpy change for each reaction a ⌬Tsolution ϭ ⌬Tmix Ϫ Tinitial b qreaction ϭ Ϫ(grams of solution ϫ specific heat of solution ϫ ⌬Tsolution) Measuring and Using Numbers What is the molar enthalpy for each of the three reactions in kJ/mol? CBL Laboratory Manual Chemistry: Matter and Change • Chapter 16 31 Name Date LAB Class CBL LABORATORY MANUAL Observing and Inferring Rearrange the equations for reactions and to obtain the equation for reaction Determine the change in enthalpy for reaction Compare this result with the enthalpy change you obtained by direct measurement Classifying Classify reactions 1, 2, and as exothermic or endothermic Error Analysis Every measurement involves a certain amount of error Which of the two values for ⌬H for reaction is likely to have the greater error? What is the largest source of error in this lab? Real-World Chemistry Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Explain how cold packs and hot packs work 32 Chemistry: Matter and Change • Chapter 16 CBL Laboratory Manual Name LAB Date Class CBL LABORATORY MANUAL Determine the Molar Mass of an Unknown Acid Use with Section 19.4 A ccording to the Arrhenius definition of acids and bases, acids are substances that produce hydrogen ions (Hϩ) in solution, and bases are substances that produce hydroxide ions (OHϪ) 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 Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc In a neutralization reaction, moles of Hϩ ions equal moles of OHϪ 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 Hϩ equal the moles of OHϪ, 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 CBL Laboratory Manual Chemistry: Matter and Change • Chapter 19 33 Name Date LAB Pre-Lab Class CBL LABORATORY MANUAL Figure A pH probe Define the following terms: (a) acid, (b) base, (c) neutralize, (d) titration, and (e) pH Write a balanced equation for the dissociation of (a) HCl, (b) H2SO4, (c) NaOH, (d) Mg(OH)2 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 Using a weighing dish, measure 0.4–0.6 g of Connect the CBL unit to the pH probe Make sure the pH probe is in channel Then, using a link cable, connect the CBL to the graphing calculator 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 Choose SET UP PROBES from the MAIN MENU Enter as the number of probes On the SELECT PROBES menu, choose pH Enter as the channel number Select USE STORED from the CALIBRATION MENU Part B: Standardizing NaOH Set up the burette, burette clamp, 250-mL Erlenmeyer flask, the CBL, and pH probe for titration as shown in Figure A Pour about 70 mL of NaOH solution into a 250-mL beaker Using a funnel, carefully fill the burette to the zero line with the NaOH solution 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 Chemistry: Matter and Change • Chapter 19 10 potassium hydrogen phthalate (KHP) Record the mass of KHP in Data Table 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 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 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 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 for the number of mL of NaOH added Always enter the total volume of NaOH that has been added to the Erlenmeyer flask CBL Laboratory Manual Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Part A: Preparing the CBL System Name Date LAB CBL LABORATORY MANUAL 11 Continue to add the NaOH solution mL at a 12 13 14 Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc 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 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 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 Fill the burette to the zero line with your stan- dardized NaOH solution 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 Dissolve the unknown acid in about 40 mL of distilled water Swirl to completely dissolve the acid Titrate the unknown acid following the procedure described in steps 2–13 of Part B Record the volume of NaOH solution in Data Table Cleanup and Disposal Rinse the beakers and Erlenmeyer flask with plenty of water If not being used again, empty the burettes and clean them according to your teacher’s directions 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) CBL Laboratory Manual Mol NaOH Mol of unknown acid Mass of unknown acid (g) Molar mass of unknown acid (g/mol) Chemistry: Matter and Change • Chapter 19 35 Name Date LAB Class CBL LABORATORY MANUAL Analyze and Conclude Measuring and Using Numbers KHP has one ionizable Hϩ ion per mole of KHP What is the ratio of moles of NaOH to moles of KHP in this reaction? Measuring and Using Numbers Determine the concentration of the NaOH solution and record it in the appropriate space in Data Table 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? 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 Why is it important to monitor the pH levels of lakes, ponds, rivers, and streams? 36 Chemistry: Matter and Change • Chapter 19 Name some common antacids and describe what ingredients make them work How they help upset stomachs? CBL Laboratory Manual Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Error Analysis If the following errors occurred, how would your calculated Name LAB Date 10 Class CBL LABORATORY MANUAL 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 Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc 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) ϫ 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 Chemistry: Matter and Change • Chapter 21 37 Name Date LAB 10 Pre-Lab Class CBL LABORATORY MANUAL Cut along dotted lines Figure A Read over the entire laboratory activity Define 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 electrons flow in a voltaic cell? Review the equation to calculate the potential of a voltaic cell Pb Zn Ag NaNO3 solution Procedure Cu Part A: Preparing the CBL System Fe Connect the CBL unit to the voltage probe Plug Part B: Data Collecting Obtain a ϫ 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) 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 Chemistry: Matter and Change • Chapter 21 Filter paper Label the ends of the filter paper with the metal 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 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 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 s and record the voltage of each of the metals compared with copper in Data Table Test the following combinations: Cu and Zn, Cu and Pb, Cu and Ag, and Cu and Fe CBL Laboratory Manual Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc the adapter cable in channel and then plug the voltage probe into the adapter cable Using a link cable, connect the CBL unit to the graphing calculator 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 Choose SET UP PROBES from the MAIN MENU Enter as the number of probes On the SELECT PROBE MENU, choose VOLTAGE Enter as the channel number Select COLLECT DATA from the MAIN MENU 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 CBL LABORATORY MANUAL 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 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 Before experimenting further, predict the potential for the combinations given in Data Table Use the information from Data Table 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 Dispose of silver and lead products in waste containers designated by your teacher Place all metal pieces in a solid-waste container Throw away filter paper and clean up the lab area Wash your hands before leaving the lab 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 Data and Observations Data Table Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Metals used Data Table Voltage Metal Reduction potential (lowest to highest) Cu/Zn Cu/Pb Cu/Ag Cu/Fe Data Table Metal Predicted potential Measured potential Percent error Zn/Pb Zn/Ag Zn/Fe Pb/Ag Pb/Fe Ag/Fe CBL Laboratory Manual Chemistry: Matter and Change • Chapter 21 39 Name Date LAB 10 Class CBL LABORATORY MANUAL Analyze and Conclude Collecting and Interpreting Data Which metal in this experiment loses electrons most readily? Which element gains electrons most readily? Observing and Inferring How your answers in question help explain the data that were recorded during this lab? Formulating Models Sketch a diagram of the flow of electrons for one of the voltaic cells Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc made in the lab Be sure to label the electrons, reduction, oxidation, cathode, and anode Thinking Critically What is the function of the NaNO3-soaked filter paper? Error Analysis What may have caused any errors found in this lab? Real-World Chemistry How lead storage batteries produce an electric current? 40 Chemistry: Matter and Change • Chapter 21 Look up a reference table of reduction poten- tials Why might they differ from your values? CBL Laboratory Manual CREDITS Art Credits Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Navta Associates: 2, 14, 18, 22, 26, 30; MacArt Design: 6, 10, 18, 34, 38 CBL Laboratory Manual Chemistry: Matter and Change 41 ...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... detergent before leaving the lab CBL Laboratory Manual Copyright © Glencoe/ McGraw-Hill, a division of the McGraw-Hill Companies, Inc LAB Class Name Date LAB Class CBL LABORATORY MANUAL Data and Observations... more times using MgCl2 CBL Laboratory Manual Copyright © Glencoe/ McGraw-Hill, a division of the McGraw-Hill Companies, Inc LAB Class Name Date LAB Class CBL LABORATORY MANUAL and AlCl3, respectively