Redox ChemistryTable of Contents

Teachers Guide pgs 2-13 Page 2 Introduction and Objectives Page 3 Activity Sequence Page 4 Organization & Materials Page 5 Student background & lesson 1 activities Page 6 Lesson 1 discussion notes Page 7 Lesson 1 practice problem with key Page 8 Lesson 2 activities with warm-up and key Page 9 Lesson 2 Activity Series Lab procedure with grading rubric Page 10 Lesson 3 Voltaic Cell Design Lab with grading rubric Pages 11-13 Assessment questions objectives 1-4

Student Guide pgs 14-18 Page 14 Student introduction, lesson 1 activities and outlines Page 15 Lesson 1 practice problems Page 16 Lesson 2 activities and warm-up Page 17 Activity Series Lab procedure with grading rubric Page 18 Lesson 3 Voltaic Cell Design Lab with grading rubric

1

Teacher’s Guide

Redox reactions in batteries

All batteries, from the one in your Ipod to the battery in your parent’s car, all work on the concept of paired reduction and oxidation reactions. An electric current is simply a flow of electrons between electrodes of two substances. This unit is designed for 12th grade IB chemistry students as part of the redox unit.

It is possible to set up cells with different substances so there is a spontaneous flow of electrons from one substance to another creating an electric current. A reduction is the gaining of electrons by an atom while oxidation is the loss of electrons of an atom. By combining the right substances a spontaneous flow of electrons can be formed in a voltaic cell. An activity series is a ranking of substances reactivity in terms of reduction and oxidation. If two materials are farther apart in an activity series there will be a greater flow of electrons between those materials. If an individual has access to an activity series they are then able to produce the most efficient battery.

In 4 hours of instruction students will learn and practice the concepts behind redox reactions and how an electric current can be created. In this lesson students will complete a variety of activities to learn and apply these concepts. Students will complete discussion notes and practice problems, as well as participate in two laboratory experiments to apply the content they have learned.

Instructional Objectives

1. Given the half reactions and standard electrode potentials of 2 half cells, draw and determine the electrode potential of the full cell.

2. Given 7 metals and their salt solutions build a set of voltaic cells to experimentally determine an activity series.

3. Given a written redox reaction equation for common metals such as Magnesium and Iron use the activity series from the IB Chemistry Data Booklet to predict the spontaneity of the reaction

4. Given common metals, their salt solutions, and access to any laboratory equipment previously used in class, design and carryout an investigation of the effect on voltage of altering one independent variable of your choice in a voltaic cell. Access to chemical supply list will also be provided.

2

Activity Sequence

1) Review reduction and oxidation reactions and the proper way to write balanced half reaction

2) Describe the concept of a standard electrode potential and how it relates to a hydrogen cell (Objective 1, 2, 3, & 4)

3) Introduce the activity series given in the Chemistry Data Booklet and discuss what the electrode potentials mean. (Objective 1, 2, & 3)a. Give practice problems involving activity series reactions

4) Diagram how to build a full voltaic cell and identifying the main regions of that cell (Objectives 1, 2, & 4)a. Give practice problems involving full voltaic cells

5) Predict spontaneity of voltaic cells using Standard Electrode Potentialsa. Give practice problems involving spontaneity (Objective 3)

6) Perform a laboratory procedure to create an activity series given 7 metals (Objective 2)

7) Perform a laboratory investigation on full voltaic cells. (Objective 4)

3

Redox in Batteries

Teacher’s Guide

OrganizationVoltaic cells in the redox topic will consist of 2 one and a half hour sessions and 1

one hour session. The first component of this lesson is to introduce students to a redox cell and to calculate standard electrode potentials. Students are expected to retain information on oxidation numbers and redox half equations for use in this unit. This first component may be extended if extra practice is needed in half reactions. The second component of this unit is to follow a standard lab procedure and determine an activity series of seven given metals. The third component of this lesson is to plan and carry out an investigation on the effect of changing an independent variable of a voltaic cell. This unit will use the standard IB lab rubric for both labs. Activity Series lab will be assessed on data collection & processing and conclusion & evaluation. Investigation of a voltaic cell will be assessed on design, data collection & processing, and conclusion & evaluation.

Materials:

Teacher’s guide: lecture notes, practice problems with answer keys, activity series lab procedure with grading rubric, and voltaic cell planning lab question and grading rubricText:

Green, John and Sadru Damji. Chemistry for the use with the International Baccalaureate Diploma Programme 2nd Edition. Victoria: IBID Press, 2001. Pgs 338-347

Hill, John, Ralph Petrucci, Terry McCreary, and Scott Perry. General Chemistry 4th Edition. New Jersey: Prentice Hall, 2005. Pgs 755-778

IB Chemistry Data Booklet

Student’s guide: Lecture outline, practice problems, activity series lab procedure with grading rubric, and voltaic cell planning lab question and grading rubricText:

Green, John and Sadru Damji. Chemistry for the use with the International Baccalaureate Diploma Programme 2nd Edition. Victoria: IBID Press, 2001. Pgs 338-347

Hill, John, Ralph Petrucci, Terry McCreary, and Scott Perry. General Chemistry 4th Edition. New Jersey: Prentice Hall, 2005. Pgs 755-778

IB Chemistry Data Booklet

4

Teacher background information

Redox chemistry is intended for Higher Level IB Chemistry students and students are expected to have mastered oxidation numbers and balancing half reactions before they move onto full cells. It is recommended that the teacher have a strong grasp of redox chemistry before delivering this lesson.

REDOX Content

Lesson 1 – Standard Electrode Potential (1.5 hour session)

Materials: Lecture notes and practice problems

Class Activities: Hand out student notes outlines Describe the concept of a standard electrode potential uses a generic metal cell:

M(s) = Mn+(aq) + ne-

Introduce how the standard electrode potential (Eθ) is calculated in comparison to a hydrogen cell.

Introduction to the activity series represented in the student Data Bookleto Identifying reducing agents and oxidizing agents in the activity serieso Practice problems looking at reduction and oxidation in an activity series

Building a voltaic cello Convert a short hand cell into a diagram and vice versao Using an activity series: determine electron flow direction, identify the

negative electrode (anode), identify the positive electrode (cathode), and determine the standard electrode potential of the cell.

o Practice problems creating voltaic cells Using half reactions of a voltaic cell and your data booklet predict spontaneity of

redox reactionso Practice problems

Assign design aspect of voltaic cell labo Students may use any lab equipment we have in the lab and any chemicals

given on the chemical inventory list available to all students Hand out Activity Series Lab Procedure

o Assign data table creation for the lab

Lecture Notes:

5

Practice problems:

6

Lesson 1 Practice ProblemsActivity series problems

Which of the following is the most powerful reducing agent? Why?Copper

MagnesiumIronZinc

In which of the following would you expect a reaction to occur? Why?Copper placed in zinc chlorideZinc placed in copper sulfate

Iron placed in magnesium sulfateMagnesium placed in sodium chloride

Answer the following:What would you expect to see happen when chlorine gas is bubbled through NaBr (aq)?

What would you expect to see happen if liquid bromine is added to NaCl (aq)?Interpret these results in terms of the power of chlorine and bromine as oxidizing and reducing agents.

You have an unknown sample of metal and an aqueous solution of its sulfate (MSO4). Describe some simple experiments to determine its reactivity to other common metals such as copper, zinc, and magnesium. Deduce a way to identify the unknown

metal with these experiments.Voltaic Cell Practice Problems

Diagram the following voltaic cell and answer the following questionsMn/Mn2+//Ag/Ag+

In order for the comparison to be of standard electrode potentials, what conditions must be met?If the experiment was meant to determine the standard electrode potential of Mn what must replace the silver electrode?

What could be used as a salt bridge?In Which direction will the electrons flow?

What will occur at the anode (identifying the half reaction)What will occur at the cathode (identifying the half reaction)

Standard Electrode Practice ProblemsWhich of the following would be best to reduce bromine? Mathematically support your answer: Iodate (V) ions (Eθ +1.19),

Copper ions (Eθ +.34), Phosphoric acid (Eθ -.28), or Hydrogen gas (Eθ -2.25)Using the Voltaic cell from the previous practice problems answer the following questions.

Calculate the cell potential.Calculate the amount of Gibb’s Free Energy

If the silver nitrate solution were diluted what would you expect to see happen to the cell potential? Why?

Practice problems answer key:

7

Lesson 2 – Creating an Activity Series (1 hour session)

Materials: Activity Series Lab Procedure and Lab supplies, and practice problems for warm-up

Class Activities: Collect Design aspect of Voltaic cell lab Copy down and solve warm-up question in notebooks Perform Activity Series Lab Assign Data Collection & Processing and Conclusion & Evaluation for the Activity

Series Lab for homework

Key to warm-up

8

Lab Grading RubricData Collection & Processing and Conclusion & Evaluation of Activity Series Lab

Lesson 3 – Investigation of a Voltaic Cell (1.5 hour session)

Activity Series Lab

Objectives:1. Successfully create a full electrochemical cell2. Predict electron flow3. Experimentally create an activity series with given metals

Pre-laboratory Activity:Read through lab and create an appropriate data table to collect raw data

Materials:Strips of the following metals: silver, copper, lead, iron, magnesium, zinc, and aluminumPowdered Silver nitrate Powdered Copper (II) nitratePowdered Lead (II) nitratePowdered Iron (III) nitratePowdered Magnesium ChloridePowdered Zinc nitratePowdered Aluminum ChlorideSteel wool7 - 50 mL beakers1 - 25 mL graduated cylinder7 - 50 mL volumetric flasks2 - Copper wire leads1 - volt-meterPaper towelsSaturated sodium chloride solutionLabeling tape

Procedure:1) Create a 1 M solution of all the powdered metal salts and place them into labeled 50 mL beakers2) Clean metal strips with steel3) Place metal strips into their own salt solution4) Attach one end of the copper lead to Silver in its salt solution and attach the other copper lead into the copper in its salt solution5) Create a salt bridge by soaking paper towel in the sodium chloride solution and connect the 2 half cells6) Attach other ends of copper leads to the volt-meter and record voltage (remember that there is a difference between a positive and negative voltage)7) Repeat steps 4-6 for all combinations of metals.8) Create a full data table9) Process data10) Write a conclusion and evaluation

9

Materials: Arrange materials requested by students for their design labs in appropriate work stations in the lab

Class Activities: Give students full class time for experimental set-up and data collection &

processing Assign data collection & processing and Conclusion & Evaluation of Voltaic Cell

Design Lab for homework.Grading Rubric Voltaic Cell Lab: Design, Data Collection & Processing, and Conclusion & Evaluation

Assessment Questions for Redox UnitObjective 1

10

1) What occurs during the operation of a voltaic cell based on the following reaction:Ni (s) + Pb 2+ (aq) Ni 2+ (aq) + Pb (s)

External Circuit Ion movement in solutionA Electrons move from Ni to Pb Pb ions move away from solid PbB Electrons move from Ni to Pb Pb ions move toward solid PbC Electrons move from Pb to Ni Ni ions move away from solid NiD Electrons move from Pb to Ni Ni ions move toward solid Ni

2) The following reactions are spontaneous as written.Fe (s) + Cd 2+ (aq) Fe 2+ (aq) + Cd (s)

Cd (s) + Sn 2+ (aq) Cd 2+ (aq) + Sn (s)

Sn (s) + Pb 2+ (aq) Pb (s) + Sn 2+ (aq)

Which of the following will react spontaneously?I. Sn (s) + Fe 2+ (aq)

II. Cd (s) + Pb 2+ (aq)

III. Fe (s) + Pb 2+ (aq)

A. I onlyB. II onlyC. III onlyD. II and III

3) From the given standard electrode potentials which statement is correct?Ca 2+ (aq) + 2e- Ca (s) Eθ = -2.87VNi 2+ (aq) + 2e- Ni (s) Eθ = -.23VFe 3+ (aq) + 1e- Fe 2+ (aq) Eθ = +.77V

A. Ca 2+ (aq) can oxidize Ni (s)B. Ni 2+ (aq) can reduce Ca 2+ (aq)C. Fe3+ (aq) can oxidize Ni (s)D. Fe 3+ (aq) can reduce Ca 2+ (aq)

4) Using the following information and arrange the metals in increasing order of reactivity

2AgNO3 (aq) + Zn (s) 2 Ag (s) + ZnNO3 (aq)ZnNO3 (aq) + Co (s) NO REACTION2AgNO3 (aq) + Co (s) CoNO3 (aq) + 2Ag (s)

A. Ag < Zn < CoB. Co < Ag < ZnC. Co < Zn < AgD. Ag < Co < Zn

5) Zinc metal can supply electrons to copper ions and magnesium metal can supply electrons to zinc ions. Which is the strongest reducing agent?

A. Copper ionsB. Zinc ion

11

C. Magnesium metalD. Zinc metal

Objective II

1) Practical assessment: Lab conclusion and evaluation for Activity Series Experiment

2) Explain how an activity series can be used to describe the reaction between an oxidizing agent and a reducing agent

3) Outline how the process of electron transfer that occurs between an oxidizing agent and a reducing agent can be used to create an activity series.

4) Use the activity series that you have created and write 3 spontaneous reactions from your data.

Objective III1) For which of the following reactions will ΔG have the greatest negative value?

A. Cu (s) + 2 Ag +(aq) 2 Ag (s) + Cu 2+ (aq) Eθ = +.46VB. Co (s) + Cu 2+ (aq) Cu (s) + Co 2+ (aq) Eθ = +.62VC. H2 (g) + Cd 2+ (aq) Cd (s) + 2H + (aq) Eθ = -.40VD Fe 2+ (aq) + Cu 2+ (aq) Fe 3+ (aq) + Cu + (aq) Eθ = -.61V

2) What combination of signs for Eθ and ΔG correspond to a spontaneous electrochemical reaction?

Eθ ΔGA + +B + -C - -D - +

3) Consider the following electrode potentialsSn 4+ (aq) + 2 e- Sn 2+ (aq) +.15VFe 3+ (aq) + 1e- Fe 2+ (aq) +.77V

What is the value of the cell potential for the spontaneous reaction?A. +1.69VB. +1.39VC. +.92VD. +.62V

4) The standard electrode potential for two half cells of iron are as follows:Fe 3+ (aq) + 1e- Fe 2+ (aq) +.77VFe 2+ (aq) + 2e- Fe (s) -.44V

12

What is the equation and the cell potential for the spontaneous reaction that occurs when the two half-cells are connected?A. 3Fe 2+ (aq) Fe (s) + 3Fe 3+ (aq) Eθ = +1.21VB. Fe 2+ (aq) + Fe 3+ (aq) 2 Fe (s) Eθ = +.33VC. Fe (s) + 2Fe 3+ (aq) 2Fe 2+ (aq) Eθ = +.33VD. Fe (s) + 2Fe 3+ (aq) 2Fe 2+ (aq) Eθ = +1.21V

Objective IV1) Practical assessment: Conclusion and evaluation of Voltaic Cell Design Lab

2) Qualitatively explain the results of changing the level of your variable on your collected data.

3) Choose a different experimental variable from the one you have already investigated and design a lab to test the effects of altering that experimental variable.

4) Predict, with explanation, what will occur by altering the variable from the previous question.

Student Guide

Student Introduction:

13

We have now spent the last week learning about reduction and oxidation reactions in isolated situations. In this part of the unit we are going to take the information we have already learned and apply it to a more practical use. We are going to look at how redox reactions can power all of the gadgets and electronics that you use everyday, from your iPod to your car. All manufactures batteries are based on the idea of redox reactions. We will not look at the specific types of batteries that run these machines, like lithium batteries, but we will look at the basic concepts of these reactions and apply them to metal / metal cells.

Lesson 1:

Materials: Lecture outline & practice problem handout Activities:

o Cover lecture contento Work practice problems

Homework: o Design for Voltaic Cell Planning Labo Data Table for Activity Series Lab

Student Notes Outline

14

Lesson 1 Practice Problems

Activity series problemsWhich of the following is the most powerful reducing agent? Why?

CopperMagnesium

IronZinc

In which of the following would you expect a reaction to occur? Why?Copper placed in zinc chlorideZinc placed in copper sulfate

Iron placed in magnesium sulfateMagnesium placed in sodium chloride

Answer the following:What would you expect to see happen when chlorine gas is bubbled through NaBr (aq)?

What would you expect to see happen if liquid bromine is added to NaCl (aq)?Interpret these results in terms of the power of chlorine and bromine as oxidizing and reducing agents.

You have an unknown sample of metal and an aqueous solution of its sulfate (MSO4). Describe some simple experiments to determine its reactivity to other common metals such as copper, zinc, and magnesium. Deduce a way to identify the unknown metal with these experiments.

Voltaic Cell Practice ProblemsDiagram the following voltaic cell and answer the following questions

Mn/Mn2+//Ag/Ag+In order for the comparison to be of standard electrode potentials, what conditions must be met?

If the experiment was meant to determine the standard electrode potential of Mn what must replace the silver electrode?What could be used as a salt bridge?

In Which direction will the electrons flow?What will occur at the anode (identifying the half reaction)

What will occur at the cathode (identifying the half reaction)

Standard Electrode Practice ProblemsWhich of the following would be best to reduce bromine? Mathematically support your answer: Iodate (V) ions (Eθ +1.19), Copper ions (Eθ +.34), Phosphoric acid (Eθ -.28), or Hydrogen gas (Eθ -2.25)

Using the Voltaic cell from the previous practice problems answer the following questions.Calculate the cell potential.

Calculate the amount of Gibb’s Free EnergyIf the silver nitrate solution were diluted what would you expect to see happen to the cell potential? Why?

15

Lesson 2 – Experimentally Determining an Activity Series

Materials: Warm-up problem & Activity Series Lab Procedure Activities:

o Collect Design for planning labo Work and review warm-up questiono Complete Activity Series Lab

Homework: o Data Collection & Processing and Conclusion & Evaluation of Activity

Series Lab

16

Activity Series Lab

Objectives:Successfully create a full electrochemical cell

Predict electron flowExperimentally create an activity series with given metals

Pre-laboratory Activity:Read through lab and create an appropriate data table to collect raw data

Materials:Strips of the following metals: silver, copper, lead, iron, magnesium, zinc, and aluminum

Powdered Silver nitrate Powdered Copper (II) nitratePowdered Lead (II) nitratePowdered Iron (III) nitrate

Powdered Magnesium ChloridePowdered Zinc nitrate

Powdered Aluminum ChlorideSteel wool

7 - 50 mL beakers1 - 25 mL graduated cylinder7 - 50 mL volumetric flasks

2 - Copper wire leads1 - volt-meterPaper towels

Saturated sodium chloride solutionLabeling tape

Procedure:Create a 1 M solution of all the powdered metal salts and place them into labeled 50 mL beakers

Clean metal strips with steelPlace metal strips into their own salt solution

Attach one end of the copper lead to Silver in its salt solution and attach the other copper lead into the copper in its salt solutionCreate a salt bridge by soaking paper towel in the sodium chloride solution and connect the 2 half cells

Attach other ends of copper leads to the volt-meter and record voltage (remember that there is a difference between a positive and negative voltage)Repeat steps 4-6 for all combinations of metals.

Create a full data tableProcess data

Write a conclusion and evaluation

Grading Rubric Activity Series – Data Collection & Processing and Conclusion & Evaluation

17

Lesson 3 – Voltaic Cell Design Lab

Materials: What you specified in your lab design Activities: Students will have the 1.5 hour session to carry-out their data collection Homework: Data Collection & Processing and Conclusion & Evaluation of

Activity Series Lab

Grading Rubric Voltaic Cell Design LabDesign, Data Collection & Processing, and Conclusion & Evaluation

18