AP Chemistry · Topic 9.10

Electrolysis and Faraday's Law Practice

Part of Applications of Thermodynamics.(ENE-6.D)

Practice questions

22

Want a predicted score for the whole AP CHEM exam? Take the 20-question diagnostic and Lumi will plan the rest.

Sample questions

5 of 22 — sign in to practice the rest with adaptive difficulty and mastery tracking.

  1. Sample 1difficulty 2/5

    The schematic shows an electrolytic cell driven by an external DC source.

    + DC anode cathode

    In an electrolytic cell, where does reduction occur?

    • A

      At the cathode (negative electrode)

      check_circle
    • B

      In the bulk solution only

    • C

      At the anode (positive electrode)

    • D

      In the salt bridge

    Why

    In electrolysis the cathode is connected to the negative terminal of the power source; cations migrate there and gain electrons (reduction).

  2. Sample 2difficulty 2/5

    Electrolysis is

    • A

      Spontaneous reaction generating current

    • B

      Forced non-spontaneous reaction using applied current

      check_circle
    • C

      Distillation

    • D

      Heating a salt

    Why

    External voltage drives a reaction with E < 0 (or ΔG > 0).

  3. Sample 3difficulty 3/5

    Electrolysis of water with inert electrodes produces

    • A

      No reaction

    • B

      H₂ at anode, O₂ at cathode

    • C

      Cl₂ at anode

    • D

      H₂ at cathode, O₂ at anode

      check_circle

    Why

    Reduction (cathode) → H₂; oxidation (anode) → O₂.

  4. Sample 4difficulty 3/5

    A student electroplates copper from 0.50 M CuSO4 onto a clean copper cathode. A constant current of 0.500 A is passed for 30.0 min. The cathode is dried and reweighed; the mass increases by 0.296 g. F = 96,485 C/mol e-. M(Cu) = 63.55 g/mol.

    anode (Cu) cathode (Cu) CuSO4 0.50 M 0.500 A 30.0 min, mass gain = 0.296 g

    How does the experimental mass of Cu deposited compare to the theoretical mass?

    • A

      Theoretical = 0.296 g; experimental should be 1/2 because Cu^2+

    • B

      Theoretical = 0.148 g; efficiency ~200%

    • C

      Theoretical = 0.296 g; experimental matches within rounding (~100% efficiency)

      check_circle
    • D

      Theoretical = 0.592 g; efficiency ~50%

    Why

    Q = It = 0.500*1800 = 900 C. mol e- = 900/96485 = 9.328e-3. mol Cu = 9.328e-3/2 = 4.664e-3. mass = 4.664e-3 * 63.55 = 0.296 g.

  5. Sample 5difficulty 3/5

    Zn (anode) Cu (cathode) eroded deposited

    During operation of a Zn|Zn²⁺ || Cu²⁺|Cu galvanic cell, what happens to electrode masses?

    • A

      Zn anode mass decreases; Cu cathode mass increases

      check_circle
    • B

      Zn gains, Cu loses

    • C

      Both gain mass

    • D

      Both electrodes lose mass

    Why

    Zn(s) → Zn²⁺ + 2e⁻ at the anode (mass decreases); Cu²⁺ + 2e⁻ → Cu(s) at the cathode (mass increases).