15 Electrochemistry Practice Problems for DAT Exam Prep

X. Electrochemistry

Electrochemistry practice problems

This chapter contains 15 practice questions on electrochemistry, including electrode reactions, galvanic and electrolytic cells, standard cell potentials, Gibbs energy, and electrolysis calculations. Allow about 1 minute per question. After completing the test, select “See Result” to view your score, answer choices, and explanations. Correct answers appear in green, and incorrect answers appear in red.

ELECTROCHEMISTRY TEST 1

1 / 15

Using the listed standard electrode potentials, which half-reaction has the greatest tendency to proceed as an oxidation at the anode? Each E° value refers to the direction shown.

A. Cd(s) → Cd²⁺(aq) + 2 e⁻; E° = +0.40 V

B. I₂(s) + 2 e⁻ → 2 I⁻(aq); E° = +0.54 V

C. 2 Cl⁻(aq) → Cl₂(g) + 2 e⁻; E° = −1.36 V

D. Mg(s) → Mg²⁺(aq) + 2 e⁻; E° = +2.37 V

E. 2 H⁺(aq) + 2 e⁻ → H₂(g); E° = 0.00 V

2 / 15

A. The strongest reducing agent among the listed species is Na⁺.

B. The strongest oxidizing agent among the listed species is Cl₂.

C. Half-reaction IV has the greatest standard tendency to proceed as a reduction.

D. Reversing half-reaction I gives the oxidation with the greatest standard tendency.

E. Combining Zn oxidation with Cu²⁺ reduction gives E°_cell = +1.10 V.

3 / 15

A. 2 Na(s) + Zn²⁺(aq) → 2 Na⁺(aq) + Zn(s)

B. Zn(s) + 2 H⁺(aq) → Zn²⁺(aq) + H₂(g)

C. 2 Na(s) + Cu²⁺(aq) → 2 Na⁺(aq) + Cu(s)

D. 2 H⁺(aq) + Cu(s) → H₂(g) + Cu²⁺(aq)

E. Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

4 / 15

Which statement is INCORRECT for the galvanic cell Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s), with E°_cell = +1.10 V?

A. The double line represents a salt bridge or equivalent liquid junction.

B. Oxidation at the anode is Zn(s) → Zn²⁺(aq) + 2 e⁻.

C. Reduction at the cathode is Cu²⁺(aq) + 2 e⁻ → Cu(s).

D. Electrons flow through the external circuit from Cu to Zn.

E. The forward cell reaction is spontaneous under standard conditions.

5 / 15

A standard cell is written as Ag(s) | Ag⁺(aq) || Cl⁻(aq) | Cl₂(g) | Pt(s), with E°_cell = +0.56 V. Given Cl₂(g) + 2 e⁻ → 2 Cl⁻(aq), E° = +1.36 V, what is the standard reduction potential x for Ag⁺(aq) + e⁻ → Ag(s)?

A. +0.40 V

B. −0.40 V

C. +0.80 V

D. −0.80 V

E. +1.60 V

6 / 15

What is E°_cell for the spontaneous galvanic cell formed from these standard reduction half-reactions?
Ag⁺(aq) + e⁻ → Ag(s), E° = +0.80 V
Cd²⁺(aq) + 2 e⁻ → Cd(s), E° = −0.40 V

A. +0.4 V

B. +1.2 V

C. -1.2 V

D. +2.0 V

E. -2.0 V

7 / 15

Which statement A–D is INCORRECT? If all four are correct, choose E.

A. For a galvanic cell operating spontaneously, the reaction Gibbs energy change is negative.

B. A Daniell cell uses a salt bridge or equivalent junction to help maintain electrical neutrality.

C. An electrolytic cell uses an external power source to drive a nonspontaneous reaction.

D. Hydrogen bubbles at the cathode can cause polarization in a simple zinc/acid voltaic cell.

E. All statements A–D are correct.

8 / 15

For a galvanic cell with a spontaneous forward reaction under standard conditions, which combination gives the signs of ΔG°, E°_cell, and the electrode polarities?

A. ΔG°: positive; E°cell: negative; anode: positive; cathode: negative

B. ΔG°: positive; E°cell: positive; anode: negative; cathode: positive

C. ΔG°: negative; E°cell: positive; anode: negative; cathode: positive

D. ΔG°: negative; E°cell: positive; anode: positive; cathode: negative

E. ΔG°: positive; E°cell: negative; anode: negative; cathode: positive

9 / 15

For an electrolytic cell driven in a nonspontaneous direction under standard conditions, which combination gives the signs of ΔG°, the cell reaction potential E°_cell, and electrode polarities? E°_cell refers to the chemical reaction, not the applied power-supply voltage.

A. ΔG°: positive; E°cell: negative; anode: positive; cathode: negative

B. ΔG°: positive; E°cell: positive; anode: positive; cathode: negative

C. ΔG°: negative; E°cell: negative; anode: positive; cathode: negative

D. ΔG°: positive; E°cell: negative; anode: negative; cathode: positive

E. ΔG°: negative; E°cell: positive; anode: negative; cathode: positive

10 / 15

For a balanced cell reaction, ΔG° = −579 kJ per mole of reaction and E°_cell = 2.00 V. What is the electron-transfer number n? Use F = 96,500 C/mol of electrons.

A. 2

B. 3

C. 4

D. 5

E. 6

11 / 15

For the electrolysis reaction Cu²⁺(aq) + 2 Cl⁻(aq) → Cu(s) + Cl₂(g), what is ΔG° per mole of reaction? Use the half-reactions below and F = 96,500 C/mol of electrons. Assume these are the selected electrode products.
Cl₂(g) + 2 e⁻ → 2 Cl⁻(aq), E° = +1.36 V
Cu²⁺(aq) + 2 e⁻ → Cu(s), E° = +0.34 V

A. +98 kJ/mol

B. −98 kJ/mol

C. +197 kJ/mol

D. −197 kJ/mol

E. +393 kJ/mol

12 / 15

A constant current of 2.5 A passes through an AgNO₃ solution for 2.0 min. How much electric charge passes through the circuit?

A. 1.25 C

B. 5 C

C. 50 C

D. 150 C

E. 300 C

13 / 15

A constant current passes for 2 h 40 min 50 s and transfers 0.010 faraday of charge. What is the current? One faraday is the charge of 1 mol of electrons; use F = 96,500 C/mol.

A. 0.010 A

B. 0.020 A

C. 0.10 A

D. 0.20 A

E. 1.0 A

14 / 15

During electrolysis of a molten magnesium salt, how many moles of Mg are produced by 3.0 faradays of charge? Assume 100% current efficiency.
Mg²⁺(l) + 2 e⁻ → Mg(l)

A. 0.7 mol

B. 1.5 mol

C. 2.0 mol

D. 3.0 mol

E. 6.0 mol

15 / 15

An aqueous NaBr solution is electrolyzed for 1 h 20 min 25 s with a constant current of 2.0 A. What volume of H₂ is produced at STP (0 °C and 1 atm)? Assume the reaction below, 100% current efficiency, F = 96,500 C/mol of electrons, and a molar gas volume of 22.4 L/mol.
2 H₂O(l) + 2 Br⁻(aq) → Br₂(l) + H₂(g) + 2 OH⁻(aq)

A. 1.1 L

B. 4.4 L

C. 8.8 L

D. 17.6 L

E. 35.2 L

Your score is

The average score is 62%

Reduction half-reaction
Oxidation and reduction

Cell notation
Oxidation and reduction
Balance electrons