Electrochemistry

Objectives:

After having completed this unit, students should be able to:

1. Define and identify oxidation and reduction – Review from Unit 3
2. Identify oxidation-reduction (redox) reactions  – Review from Unit 3
3. Assign oxidation states to the elements in a compound or ion.  – Review from Unit 3
4. Identify oxidizing and reducing agents.  – Review from Unit 3
5. Diagram and describe and explain voltaic (or galvanic) and electrolytic cells: indicate the cathode, anode, salt bridge, direction of flow of electrons, direction of migration of ions and the half-cell reaction involved at each electrode.
6. Write voltaic cells using standard line notation.
7. Define cell potential and explain how it is measured.
8. Define standard reduction potential.
9. Explain how standard reduction potentials are assigned in terms of the standard hydrogen electrode.
10. Using tabulated standard reduction potential calculate the standard cell potential (standard EMF) of a galvanic cell and predict whether the reaction is spontaneous.
11. Given the components of the electrodes and observations on what happens at the electrodes in a voltaic cell, write the balanced oxidation and reduction half reactions, write the balanced overall spontaneous reaction, and calculate the cell voltage
12. Using standard reduction potentials predict the strength of various oxidizing and reducing agents.
13. Explain the relationship between the maximum cell potential and the free energy difference between cell reactants and products.
14. Know and be able to use the equations that relate ΔG°, K and E° for cell reactions.
15. Explain the basis for concentration cells.
16. Qualitatively predict the effect of concentration and gas pressure on cell potential.
17. Use the Nernst equation to calculate the EMF under nonstandard conditions or to calculate a concentration of reactant or product required to give a certain voltage.
18. Explain with the aid of the balanced equation the operation of fuel cells and of the lead-acid, alkaline, the nickel-cadmium, nickel-metal hydride, and lithium-ion batteries.
19. Distinguish between batteries and fuel cells.
20. Explain the electrochemical nature of corrosion and describe some methods of preventing it.
21. Explain the difference in product at each electrode for molten salts compared to aqueous solutions of the salt.
22. Using standard reduction potentials predict the most likely product at each electrode in the electrolysis of aqueous solutions and write the equation for the reaction.
23. Given two of the three following variables: time, current or amount of substances reacting in an electrolytic cell, calculate the third variable. Amount can be indicated by grams, volume, moles, concentration, pH, pOH, molar mass, or oxidation state
24. Explain how electrolysis can be used in the application of metal plating.

Reading and Homework Exercises

Table of Contents from: OpenStax Chemistry 2e:

Introduction

17.1 Review of Redox Chemistry

17.2 Galvanic Cells

An electrochemical cell has a solid zinc anode in Zn(NO₃)₂ and a solid copper cathode in Cu(NO₃)₂.  Answer the following questions about this cell:

Question 1:

Question 2:

Question 3:

A galvanic cell is based on the reaction:

8 H⁺ + 5 Fe²⁺ + MnO₄^– → 5 Fe³⁺ + Mn²⁺ + 4 H₂O

Answer the following questions:

Question 4:

Question 5:

Question 6:

Question 7:

17.3 Electrode and Cell Potentials

An electrochemical cell has a solid zinc anode in Zn(NO₃)₂ and a solid copper cathode in Cu(NO₃)₂.  Answer the following question about this cell using data in Table 17.1

Question 8:

A galvanic cell is based on the reaction:

8 H⁺ + 5 Fe²⁺ + MnO₄^– → 5 Fe³⁺ + Mn²⁺ + 4 H₂O

Answer the following question about this cell using data in Table 17.1

Question 9:

A galvanic cell (spontaneous) is set up with the Pb/Pb²⁺ and Ag/Ag⁺ couples.  Answer the following questions (use data in Table 17.1)

Question 10:

Question 11:

Question 12:

Question 13:

Answer the following 3 questions for the following redox reaction:

2 Au³⁺ + 3 Ni(OH)₂ + 6 OH^– → 2 Au + 3 NiO₂ + 6 H₂O

Question 14:

Question 15:

Question 16:

Use a table of standard reduction potentials to answer the following two questions:

Question 17:

Question 18:

17.4 Potential, Free Energy, and Equilibrium

A galvanic cell is based on the reaction:

8 H⁺ + 5 Fe²⁺ + MnO₄^– → 5 Fe³⁺ + Mn²⁺ + 4 H₂O

Answer the following question:

Question 19:

Answer the following  question for the following redox reaction:

2 Au³⁺ + 3 Ni(OH)₂ + 6 OH^– → 2 Au + 3 NiO₂ + 6 H₂O

Question 20:

Answer the following  2 questions for the following redox reaction:

3 Cu²⁺ + 2 NO + 4 H₂O → 3 Cu + 8 H⁺ + 2 NO₃^–

Question 21:

Question 22:

Calculate the E_cell in volts of a Zn-Ag⁺ cell under the following nonstandard conditions as listed in the problem below::

Zn(s) + 2Ag⁺ (aq) —-> Zn²⁺ (aq) + 2Ag(s)

Question 23:

For the same cell, answer the following question:

Question 24:

17.5 Batteries and Fuel Cells

Question 25:

Question 26:

Question 27:

Question 28:

17.6 Corrosion

Question 29:

Question 30:

17.7 Electrolysis

Question 31:

Question 32:

Question 33:

Question 34:

Question 35:

Question 36:

Question 37:

Question 38:

Question 39:

Question 40:

Question 41: