Question 1

Which statement best describes the role of the reducing agent in a redox reaction?

Accepted Answer

It loses electrons and is oxidized.

Question 2

In the reaction $$\mathrm{Fe(s) + Cu$$^{2+}$$(aq) \rightarrow Fe$$^{2+}$$(aq) + Cu(s)}$$, which species is the oxidizing agent?

Accepted Answer

$$Cu^{2+}(aq)$$

Question 3

What is the oxidation number of nitrogen in $$\mathrm{N_2O_5}$$?

Accepted Answer

+5

Question 4

Which of the following is the correct balanced half-reaction for the reduction of $$\mathrm{Cu$$^{2+}$$(aq)} to$$ $$\mathrm{Cu(s)}$$?

Accepted Answer

$$\mathrm{Cu$$^{2+}$$(aq) + 2e^- \rightarrow Cu(s)}$$

Question 5

When balancing a redox reaction in basic solution, which step is unique compared to balancing in acidic solution?

Accepted Answer

Add $$\mathrm{OH^-}$$ ions to both sides to neutralize $$\mathrm{H^+}$$ ions.

Question 6

Given the standard reduction potentials: $$\mathrm{Ag^+(aq) + e^- \rightarrow Ag(s)}$$ $$E^\circ = +0.80\ \mathrm{V}$$ and $$\mathrm{Cu$$^{2+}$$(aq) + 2e^- \rightarrow Cu(s)}$$ $$E^\circ = +0.34\ \mathrm{V}$$, which is the stronger oxidizing agent?

Accepted Answer

Ag^+(aq)

Question 7

Which of the following reactions is spontaneous at 25°C, given the standard reduction potentials below?
$$\mathrm{Ag^+(aq) + e^- \rightarrow Ag(s)}$$ $$E^\circ = +0.80\ \mathrm{V}$$
$$\mathrm{Cr$$^{3+}$$(aq) + 3e^- \rightarrow Cr(s)}$$ $$E^\circ = -0.74\ \mathrm{V}$$

Accepted Answer

$$\mathrm{Ag^+(aq) + Cr(s) \rightarrow Ag(s) + Cr$$^{3+}$$(aq)}$$

Question 8

What is the standard cell potential, $$E^\circ_{cell}$$, for the reaction $$\mathrm{Sn(s) + Pb$$^{2+}$$(aq) \rightarrow Sn$$^{2+}$$(aq) + Pb(s)}$$ given:
$$\mathrm{Sn$$^{2+}$$(aq) + 2e^- \rightarrow Sn(s)}$$ $$E^\circ = -0.14\ \mathrm{V}$$
$$\mathrm{Pb$$^{2+}$$(aq) + 2e^- \rightarrow Pb(s)}$$ $$E^\circ = -0.13\ \mathrm{V}$$

Accepted Answer

$$E^\circ_{cell} = +0.01\ \mathrm{V}$$

Question 9

Which equation correctly relates the standard cell potential to the standard Gibbs free energy change?

Accepted Answer

$$\Delta G^\circ = -nFE^\circ_{cell}$$

Question 10

A lithium-ion battery operates by the following half-reactions:
Anode: $$\mathrm{Li(s) \rightarrow Li^+(aq) + e^-}$$
Cathode: $$\mathrm{$$CoO_2$$(s) + Li^+(aq) + e^- \rightarrow $$LiCoO_2$$(s)}$$
What is the correct cell notation?

Accepted Answer

$$\mathrm{Li(s) | Li^+(aq) || Li^+(aq), $$CoO_2$$(s) | $$LiCoO_2$$(s)}$$

Question 11

Which of the following best describes the function of a salt bridge in a galvanic cell?

Accepted Answer

It maintains electrical neutrality by allowing ion flow.

Question 12

Calculate the equilibrium constant, $$K$$, for the reaction $$\mathrm{2Ag(s) + Fe$$^{2+}$$(aq) \rightarrow 2Ag^+(aq) + Fe(s)} at 25$$°C, given:
$$\mathrm{Fe$$^{2+}$$(aq) + 2e^- \rightarrow Fe(s)}$$ $$E^\circ = -0.44\ \mathrm{V}$$
$$\mathrm{Ag^+(aq) + e^- \rightarrow Ag(s)}$$ $$E^\circ = +0.80\ \mathrm{V}$$

Accepted Answer

$$K = 1.0 	imes 10$$^{41}$$

Question 13

Which battery type uses the following overall reaction?
$$\mathrm{Zn(s) + 2MnO_2(s) \rightarrow ZnO(s) + Mn_2O_3(s)}$$

Accepted Answer

Alkaline battery

Question 14

If the cell reaction is $$\mathrm{Fe$$^{2+}$$(aq) + Cd(s) \rightarrow Fe(s) + Cd$$^{2+}$$(aq)}$$ and $$[Fe$$^{2+}$$] = 0.60\ \mathrm{M}$$, $$[Cd$$^{2+}$$] = 0.010\ \mathrm{M} at 25$$°C, what is the cell potential ($$E_{cell}$$)?
Given:
$$\mathrm{Fe$$^{2+}$$(aq) + 2e^- \rightarrow Fe(s)}$$ $$E^\circ = -0.44\ \mathrm{V}$$
$$\mathrm{Cd$$^{2+}$$(aq) + 2e^- \rightarrow Cd(s)}$$ $$E^\circ = -0.40\ \mathrm{V}$$

Accepted Answer

$$E_{cell} = -0.06\ \mathrm{V}$$

Question 15

Which of the following statements about standard reduction potentials is TRUE?

Accepted Answer

All standard reduction potentials are measured relative to the standard hydrogen electrode.

Question 16

Which of the following is the correct Nernst equation for a cell at 25°C?

Accepted Answer

$$E_{cell} = E^\circ_{cell} - \frac{0.0257}{n} \ln Q$$

Question 17

In a lead storage battery, which half-reaction occurs at the cathode during discharge?

Accepted Answer

$$\mathrm{$$PbO_2$$(s) + 4H^+(aq) + SO_4$^{2-}(aq) + 2e^- \rightarrow $$PbSO_4$$(s) + 2H_2O(l)}$$

Question 18

Which of the following is a correct statement about the relationship between $$K$$, $$E^\circ_{cell}$$, and $$\Delta G^\circ$$ under standard conditions?

Accepted Answer

If $$E^\circ_{cell} = 0$$, then $$K = 1$$ and $$\Delta G^\circ = 0.$$

Electrochemistry: Redox Reactions, Oxidation Numbers, and Balancing

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