Ch.18 - ElectrochemistryWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Galvanic (Voltaic Cells) & Electrolytic Cells

Concept #1: Galvanic versus Electrolytic Cells

Concept #2: An electrolytic cell presents an electrochemical cell that is nonspontaneous. 

Example #1: A certain electrochemical cell involves a five electron change and has a value of Keq = 3.0 x 1016 at 298 K. The value of ΔHo for the reaction is -68.3 kJ/mol. Calculate the values of ΔGo, ΔEo, for a standard electrochemical cell constructed based on this reaction and also ΔSo for the reaction.

Practice: Given the following standard reduction potentials,

Hg22+(aq)  +  2 e    2 Hg (?)                                                          E° = +0.789 V

 

Hg2Cl2(s)  +  2 e    2 Hg (?)  +  2 Cl-(aq)                                        E° = +0.271 V

determine Ksp for Hg2Cl2(s) at 25 °C.

Example #2: The cell notation for a redox reaction is given as the following at (T = 298 K):

Zn (s) Ι Zn2+ (aq, 0.37 M) ΙΙ Ni2+ (aq, 0.059 M) Ι Ni (s)

a)  Write the balanced half-reactions occurring at the anode and the cathode.

b)  Write out the complete balanced redox reaction.

c)  Determine the Eo cell.

d)  Calculate the maximum electrical work that can be produced by this cell.

e)  Calculate the reactant quotient, Q, for this cell and the cell potential under non-standard conditions.

 

Example #3: Answer each of the following questions based on the following half reactions:

HALF REACTIONS                                Eo (V)

Cl2 (g)  +  2 e            2 Cl (aq)          + 1.36

l2 (g)  +  2 e              2 l (aq)             + 0.535

Pb2+ (aq)   +  2 e      Pb (s)                  - 0.126

V2+ (aq)  +  2 e         V (s)                    - 1.18

a)  Which is the strongest oxidizing agent?

b)  Which is the strongest reducing agent?

c)  Will I (aq) reduce Cl2 (g) to Cl (g)?

Example #4: Electric current, or flow of electrons is measured in Amperes (A). One Ampere is the delivery of one coulomb (C) of charge per second. What mass of Zinc (in g) is oxidized (to Zn2+) by a dry cell battery that supplies 125 mA of current for two hours (recall that Faraday's constant is the charge in coulombs on a mole of electrons)? 

Example #5: Consider the combustion of formaldehyde CH2O and the data below for the following five questions.

            I. CH2O (g)  + O(g)   →   CO(g)  +  H2O (l)

            II. 4H+  +  4 e -  +  O(g)   →   2 H2O (l)                              ΔE° = 1.23V

Which compound is reduced in reaction I?

{C}a.    {C}CH2O

{C}b.    {C}H2O

{C}c.    {C}O2

{C}d.    {C}CO2

{C}e.    {C}None of these

What is the change in oxidation number of the carbon in reaction I?

{C}a.    {C}-4

{C}b.    {C}-1

{C}c.    {C}0

{C}d.    {C}1

{C}e.    {C}4

Example #6: The purpose of a galvanic cell is to:

a. Transduce chemical energy to electrical energy.

b. Purify solids.

c. Allow for oxidation without reduction.

d. To consume electricity. 

Example #7: During the process for electrolysis of water a current is passed through water and produces hydrogen gas and oxygen gas. Which of the following statements is true?

a. O2 gas is produced at the anode.

b. H2 gas is produced at the cathode.

c. In the reaction, H2 moles are twice the O2 moles.

d. All of the following are correct. 

Example #8: Which statement is false?

a. Reduction occurs at the cathode.

b. A reducing agent will lose electrons.

c. Cations migrate to the cathode in both electrolytic and electrochemical cells.

d. Li (s) is the strongest oxidizing agent; F2 is the strongest reducing agent. 

Example #9: Which of the following reactions may occur at the anode? 

a. Ga3+ (aq)  +  3 e   →   Ga (s) 

b. Cu2+ (aq)  +  2 e   →   Cu (s) 

c. 2 Cl (aq)    →   Cl2 (g)  +  3 e 

d. Co (s)  +  e   →   Co+ (aq) 

Example #10: Define a salt bridge.

A) A pathway, composed of salt water, that ions pass through.

B) A pathway in which no ions flow.

C) A pathway between the cathode and anode in which ions are reduced.

D) A pathway between the cathode and anode in which ions are oxidized.

E) A pathway by which counterions can flow between the half-cells without the solutions in the half-cell totally mixing.

Example #11: What statement is NOT true about standard electrode potentials?

A) E°cell is positive for spontaneous reactions.

B) Electrons will flow from more negative electrode to more positive electrode.

C) The electrode potential of the standard hydrogen electrode is exactly zero.

D) E°cell is the difference in voltage between the anode and the cathode.

E) The electrode in any half-cell with a greater tendency to undergo reduction is positively charged relative to the standard hydrogen electrode and therefore has a positive E°.

Example #12: Use the standard reduction potentials below to determine which element or ion is the best reducing agent.

Pd2+ (aq)  +  2 e  →  Pd (s)               Eo = + 0.90 V

2 H+ (aq)  +  2 e  →  H2 (g)               Eo =    0.00 V

Mn2+ (aq)  +  2 e  →  Mn (s)               Eo = - 1.18 V

a) Pd (s)              b) H+ (aq)              c) Mn2+ (aq)              d) H2 (g)

Example #13: Consider an electrochemical cell where the following reaction takes place:

Na2O (aq) + Ba (s)  →  2 Na (s) + BaO (aq)

What is the cell notation for this cell? 

 

What is the ratio of oxidizing agent to reducing agent? 

Additional Problems
Draw an electrolytic cell in which Mn2+ is reduced to Mn and Sn is oxidized to Sn2+. Label the anode and cathode, indicate the direction of electron flow, and write an equation for the half-reaction occurring at each electrode. What minimum voltage is necessary to drive the reaction?
Which of the following general statements (in a‐c) are FALSE? a) Oxidation occurs at the anode of a voltaic cell b) The potential of a cell depends on its temperature c) A functioning voltaic cell has a negative emf d) Both statements a and b are false e) All statements a, b, and c are false
Complete the following statement: In a galvanic cell, the anions migrate toward the (anode/cathode) and the electrons flow through an external circuit from the (anode/cathode) to the (anode/cathode).
Consider the molecular view of an electrochemical cell involving the overall reaction: Zn(s) + Ni2+(aq) → Zn2+(aq) + Ni(s) Draw a similar sketch of the cell after it has generated a substantial amount of electrical current.
What is the balanced half‐reaction that occurs at the anode in the unbalanced overall cell reaction of a voltaic cell: 3 MnO4– + 5 Fe (s) → 3 Mn2+ + 5 Fe3+ a) MnO 4- (aq) + 8H (aq) + 5e - → Mn2+ (aq) + 4H 2 O(l)  b) 2MnO 4- (aq) +12H+ (aq) + 6e - → 2Mn2+ (aq) + 3H 2 O(l) c) Fe(s) → Fe3+ (aq) + 3e - d) Fe(s) → Fe2+ (aq) + 2e - e) Fe2+ (s) → Fe3+ (aq) + e -    
Identify the location of oxidation in an electrochemical cell. A) the salt bridge B) the socket C) the electrode D) the anode E) the cathode
The purpose of a galvanic cell is to: a. Transduce chemical energy to electrical energy. b. Purify solids. c. Allow for oxidation without reduction. d. To consume electricity. 
Which statement is false? a. Reduction occurs at the cathode. b. A reducing agent will lose electrons. c. Cations migrate to the cathode in both electrolytic and electrochemical cells. d. Li (s) is the strongest oxidizing agent; F2 is the strongest reducing agent. 
Define a salt bridge.   A) A pathway, composed of salt water, that ions pass through. B) A pathway in which no ions flow. C) A pathway between the cathode and anode in which ions are reduced. D) A pathway between the cathode and anode in which ions are oxidized. E) A pathway by which counterions can flow between the half-cells without the solutions in the half-cell totally mixing.
What statement is NOT true about standard electrode potentials? A) E°cell is positive for spontaneous reactions. B) Electrons will flow from more negative electrode to more positive electrode. C) The electrode potential of the standard hydrogen electrode is exactly zero. D) E°cell is the difference in voltage between the anode and the cathode. E) The electrode in any half-cell with a greater tendency to undergo reduction is positively charged relative to the standard hydrogen electrode and therefore has a positive E°.
Which statement is true of all functioning voltaic cells? a) Both Ecell and ∆G are negative b) Both Ecell and ∆G are positive c) Ecell is negative and ∆G is positive d) Ecell is positive and ∆G is negative e) None of the above must be true
What is the name given to the experimental apparatus for generating electricity through the use of a spontaneous reaction? A) electrolytic cell B) galvanic cell C) fuel cell D) cathodic cell E) anodic cell
Choose the correct statement. A) The cathode is the electrode where the oxidation takes place. B) The cathode is the electrode where the reduction takes place. C) Both oxidation and reduction may take place at the cathode, depending on the cell. D) The cathode is always positive. E) The anode is always negative.
When designing a voltaic cell with the following cell notation:                         Li(s) | Li+(aq) ‖ Zn2+(aq) | Zn(s) That uses a salt bridge made of NaCl, what answer describes what is occurring at the anode? A.  Lithium is being oxidized and Cl − joins the solution B.  Lithium is being reduced and Cl − joins the solution C.  Zinc is being oxidized and Cl− joins the solution D.  Zinc is being oxidized and Na+ joins the solution E.  Lithium is being oxidized and Na+ joins the solution
Sketch a voltaic cell for each redox reaction. Label the anode and cathode and indicate the half-reaction that occurs at each electrode and the species present in each solution. Also indicate the direction of electron flow. a. Ni2+(aq) + Mg(s) → Ni(s) + Mg2+(aq)  
Sketch a voltaic cell for each redox reaction. Label the anode and cathode and indicate the half-reaction that occurs at each electrode and the species present in each solution. Also indicate the direction of electron flow. b. 2 H+(aq) + Fe(s) → H 2(g) + Fe2+(aq)  
Sketch a voltaic cell for each redox reaction. Label the anode and cathode and indicate the half-reaction that occurs at each electrode and the species present in each solution. Also indicate the direction of electron flow. c. 2 NO3– (aq) + 8 H+(aq) + 3 Cu(s) → 2 NO(g) + 4 H 2O (/) + 3 Cu2+(aq)  
Consider the voltaic cell: a. Determine the direction of electron flow and label the anode and the cathode. b. Write a balanced equation for the overall reaction and calculate E°cell. c. Label each electrode as negative or positive.  d. Indicate the direction of anion and cation flow in the salt bridge.
Design a voltaic cell from the following half-reactions: Cr 2O 7(aq) + 14 H +(aq) + 6 e − → 2 Cr 3+ (aq) + 7 H 2O(l)              E  o = 1.33 O 2(g) + 4 H +(aq) + 4 e − → H 2O(l)                                                 E     o = 1.23 In the overall reaction, how many H + ions would be shown and which side would they be on? A. 18 on the left B. 16 on the left C. 10 on the left D. 10 on the right E. 12 on the right  
What is the name given to the experimental apparatus for generating electricity through the use of a spontaneous reaction? a) electrolytic cell b) voltaic cell c) fuel cell d) standard cell e) anode cell
Make a sketch of a concentration cell employing two Zn/Zn2+ half-cells. The concentration of Zn2+ in one of the half-cells is 2.0 M and the concentration in the other half-cell is 1.0 X 10–3 M. Label the anode and the cathode and indicate the half-reaction occurring at each electrode . Also indicate the direction of electron flow.
Consider the concentration cell: a. Label the anode and cathode. b. Indicate the direction of electron flow. c. Indicate what happens to the concentration of Pb2+ in each half-cell.
Consider the electrolytic cell:a. Label the anode and the cathode and indicate the halfreactions occurring at each.b. Indicate the direction of electron flow.c. Label the terminals on the battery as positive or negative and calculate tbe minimum voltage necessary to drive the reaction.
In this electrochemical cell, what is the anode? 1. The solid zinc electrode  2. The Zn2+(aq) ions in the 1 M solution 3. The Cu2+(aq) ions in the 1 M solution 4. The solid copper electrode
a. Label the anode and the cathode. Indicate the direction of electron flow. Label the terminals on the battery as positive or negative.b. Indicate the half-reaction occurring at Anode. Express your answer as a chemical equation. Identify all of the phases in your answer.c. Indicate the half-reaction occurring at Cathode. Express your answer as a chemical equation. Identify all of the phases in your answer.d. Calculate the minimum voltage necessary to drive the reaction. Express your answer using two significant figures.
During operation: which half-reaction occurs at the cathode in each type of cell:a. In a battery (voltaic or galvanized cell) reduction occurs at the cathode or oxidation occurs at the cathodeb. In an electrolyte cell reduction occurs at the cathode or oxidation occurs at the cathode
Fluoride ion in aqueous are difficult to oxidize at the anode of an electrolytic cell because(A) the aqueous solutions of fluorides are nonconducting.(B) it is impossible to find the proper material from which to build the electrodes.(C) the fluorides are not very soluble.(D) oxygen is released from water in preference to fluorine.
Label the diagram according to the components and processes of a voltaic cell. Drag the appropriate labels to their respective targets.
What is produced at each electrode in the electrolysis of an aqueous solution of both NaBr and AgF? Drag the appropriate items to their respective bins. Na(s), H2(g), Ag(s), F2(g), O2(g), Br2(l)
a. In an electrolytic cell Mn2+ is reduced to Mn and Sn is oxidized to Sn2+. Write an equation for the half-reaction occurring at the anode and at the cathode.b. What is the minimum voltage required to drive the reaction in part a.
Which of the following statements is true concerning the voltaic cell shown below? a. The Zn anode mass decreases as the cell discharges.b. The Zn anode mass increases as the cell discharges. c. The Zn cathode mass increases as the cell discharges.d. The Zn cathode mass decreases as the cell discharges. e. The mass of the Zn electrode neither increases nor decreases as the cell discharges.