9.11 Practice Problems

Attempt these problems as if they were real exam questions in an exam environment.

Only look up information if you get severely stuck. Never look at the solution until you have exhausted all efforts to solve the problem.

  1. How many water molecules appear in the fully, balanced reaction (in an acidic solution) for the following redox reaction?

    \[\mathrm{Cu}(s) + \mathrm{Ag^+}(aq) \longrightarrow \mathrm{Cu^{2+}}(aq) + \mathrm{Ag}(s)\]

    1. 0
    2. 1
    3. 2
    4. 3

    Solution


  2. What is E°cell (in V) for the following cell diagram?

    \[\mathrm{Ag}(s) ~|~ \mathrm{Ag^+}(aq) ~||~ \mathrm{Cu^+}(aq) ~|~ \mathrm{Cu}(s)\]

    Refer to the standard reduction potential table.

    1. –0.46
    2. –0.28
    3. 0.28
    4. 1.32

    Solution


  3. What is E°cell (in V) for the following cell diagram?

    \[\mathrm{Zn}(s) ~|~ \mathrm{Zn^{2+}}(aq) ~||~ \mathrm{Cu^{2+}}(aq) ~|~ \mathrm{Cu}(s)\]

    Refer to the standard reduction potential table.

    1. –1.10
    2. 0.34
    3. 1.10
    4. 1.32

    Solution


  4. What is the oxidizing and reducing agent, respectively, in the following galvanic cell?

    \[\mathrm{In}(s) ~|~ \mathrm{In^{3+}}(aq) ~||~ \mathrm{Cu^+}(aq) ~|~ \mathrm{Cu}(s)\]

    1. In, Cu
    2. Cu, In

    Solution


  5. Choose the incorrect statement regarding a galvanic cell.

    1. Anions are supplied to the cathode from the salt bridge.
    2. Electrons flow from anode to cathode.
    3. Reduction takes place at the cathode.
    4. An inert electrode does not gain mass.

    Solution


  6. An unknown electrode made of a pure metal is paired with a standard hydrogen electrode in a galvanic cell (at 25 °C). You notice the unknown electrode losing mass during the reaction. The standard cell potential is measured to be +1.18 V. What is the metal of the unknown electrode? Refer to the standard reduction potential table.

    1. Ag
    2. Mg
    3. Mn
    4. Pb

    Solution


  7. How many moles of electrons are transferred in the following reaction?

    1. 2
    2. 3
    3. 4
    4. 6

    Solution


  8. What is Ecell (in V) for the following redox system (at 25 °C)?

    \[\mathrm{Zn}(s) ~|~ \mathrm{Zn^{2+}}(aq, 0.05~M) ~||~ \mathrm{Zn^{2+}}(aq, 1.3~M) ~|~ \mathrm{Zn}(s)\]

    1. –0.012
    2. 0.0
    3. 0.042
    4. 1.03

    Solution


  9. An unknown electrode made of a pure metal is paired with a pure zinc electrode. A galvanic cell is created under standard conditions. The standard cell potential is measured to be 0.00 V. What is the metal of the unknown electrode?

    1. Pb
    2. Zn
    3. Ag
    4. Mg

    Solution


  10. How many total water molecules are present when the following redox reaction is balanced for a basic solution?

    \[\mathrm{Fe}(s) + \mathrm{Cr_2O_7}^{2-}(aq) \longrightarrow \mathrm{Fe^{3+}}(aq) + \mathrm{Cr}^{3+}(aq)\]

    1. 2
    2. 4
    3. 7
    4. 14

    Solution


  11. Molten ZnCl2 is electrolyzed to Zn(s) by applying 25.0 A of current for 30 min in an electrolytic cell. How much Zn (in g) is produced?

    1. 3.54
    2. 10.38
    3. 15.24
    4. 21.48

    Solution


  12. Which of the following represents a reaction that is not spontaneous?

    1. ΔG < 0
    2. Ecell < 0
    3. Ecell > 0
    4. ΔSuniverse > 0

    Solution


  13. What is the oxidizing agent in the following chemical reaction?

    \[\mathrm{Cu}(s) + \mathrm{Ag^+}(aq) \longrightarrow \mathrm{Cu^{2+}}(aq) + \mathrm{Ag}(s)\]

    1. copper
    2. silver
    3. water
    4. none of these

    Solution


  14. How many moles of electrons are transferred in the following redox reaction?

    \[\mathrm{Ni}(s) + \mathrm{Au^{3+}}(aq) \longrightarrow \mathrm{Ni^{2+}}(aq) + \mathrm{Au}(s)\]

    1. 1
    2. 3
    3. 4
    4. 6

    Solution


  15. Determine the equilibrium constant for the following redox reaction (at 25°C). Refer to the standard reduction potential table.

    \[\mathrm{Fe}(s) + \mathrm{2Ag^+}(aq) \rightleftharpoons \mathrm{Fe^{2+}}(aq) + \mathrm{2Ag}(s)\]

    1. 3.43 × 10–34
    2. 1.25
    3. 9.28 × 1024
    4. 1.70 × 1042

    Solution


  16. A galvanic cell has a standard cell potential of 0.43 V (at 25 °C). The corresponding equilibrium constant is 2.1 × 1022. How many moles of electrons are transferred in this redox reaction?

    1. 0
    2. 3
    3. 4
    4. 6

    Solution


  17. Molten ZnCl2 is electrolyzed to Zn(s) by applying 30.0 A of current for 20 minutes in an electrolytic cell. How much Zn (in g) is produced?

    1. 3.5
    2. 12.2
    3. 15.2
    4. 21.5

    Solution




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