Question 1

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

Accepted Answer

It maintains electrical neutrality by allowing the flow of ions between the half-cells.

Question 2

Given the cell notation $$\mathrm{Zn(s)\ |\ Zn$$^{2+}$$(aq,\ 1\ M)\ ||\ Cu$$^{2+}$$(aq,\ 1\ M)\ |\ Cu(s)}$$, which species is oxidized and which is reduced?

Accepted Answer

Cu is reduced; Zn is oxidized.

Question 3

What is the standard cell potential ($$E^\circ_{cell}) $$for the reaction $$\mathrm{Cu$$^{2+}$$(aq) + Zn(s) \rightarrow Cu(s) + Zn$$^{2+}$$(aq)}$$ given $$E^\circ (\mathrm{Cu$$^{2+}$$/Cu}) = 0.34\ V$$ and $$E^\circ (\mathrm{Zn$$^{2+}$$/Zn}) = -0.76\ V$$?

Accepted Answer

$$E^\circ_{cell} = 0.34\ V - (-0.76\ V) = 1.10\ V$$

Question 4

Which of the following correctly identifies the anode and cathode in a galvanic cell?

Accepted Answer

Anode: site of oxidation; Cathode: site of reduction

Question 5

A student is asked to balance the following redox reaction in acidic solution: $$\mathrm{$$MnO_4$$^- + Fe$$^{2+}$$ \rightarrow Mn$$^{2+}$$ + Fe$$^{3+}$$}. $$What is the correct number of electrons transferred in the balanced equation?

Accepted Answer

5 electrons

Question 6

Which of the following changes will increase the cell potential ($$E) $$for a galvanic cell based on the Nernst equation?

Accepted Answer

Increasing the concentration of reactants

Question 7

For the reaction $$\mathrm{2H_2O(l) \rightarrow 2H_2(g) + O_2$(g)}$$ occurring in an electrolytic cell, which statement is correct?

Accepted Answer

The reaction is nonspontaneous and requires an external power source.

Question 8

Which of the following is the correct expression for the Nernst equation at 25°C ($$298\ K$$)?

Accepted Answer

$$E = E^\circ - \frac{0.0592}{n} \log Q$$

Question 9

A battery is constructed using the following half-cells: $$\mathrm{Ag^+ + e^- \rightarrow Ag}$$ ($$E^\circ = 0.80\ V) $$and $$\mathrm{Cu$$^{2+}$$ + 2e^- \rightarrow Cu}$$ ($$E^\circ = 0.34\ V). $$What is the overall cell reaction and its standard cell potential?

Accepted Answer

$$\mathrm{Cu(s) + 2Ag^+ (aq) \rightarrow Cu$$^{2+}$$(aq) + 2Ag(s)}$$, $$E^\circ_{cell} = 0.46\ V$$

Question 10

Which of the following best describes the relationship between Gibbs free energy and cell potential?

Accepted Answer

$$\Delta G^\circ = -nFE^\circ$$

Question 11

In a redox reaction, which species acts as the oxidizing agent?

Accepted Answer

The species that gains electrons

Question 12

A galvanic cell is constructed with the following half-cells: $$\mathrm{Fe$$^{2+}$$/Fe}$$ ($$E^\circ = -0.44\ V) $$and $$\mathrm{Pb$$^{2+}$$/Pb}$$ ($$E^\circ = -0.13\ V). $$Which metal will be the anode?

Accepted Answer

Fe

Question 13

If the cell potential ($$E_{cell}) $$for a reaction is negative, what can be concluded about the reaction?

Accepted Answer

The reaction is nonspontaneous as written.

Question 14

Which of the following is true for the oxidation number of hydrogen in $$\mathrm{NaH}$$?

Accepted Answer

-1

Question 15

A solution contains $$\mathrm{Cl_2$}$$ and $$\mathrm{Br^-}. $$Which species will be reduced if both are present in an electrochemical cell?

Accepted Answer

$$\mathrm{Cl_2$}$$

Question 16

Which of the following best explains why platinum (Pt) is used as an electrode in some electrochemical cells?

Accepted Answer

Pt is inert and conducts electrons without participating in the reaction.

Question 17

If the equilibrium constant $$K$$ for a redox reaction is much greater than 1, what can be said about $$E^\circ_{cell}$$?

Accepted Answer

$$E^\circ_{cell} is $$positive

Question 18

Which of the following is the correct shorthand notation for a cell where iron is oxidized and silver is reduced?

Accepted Answer

$$\mathrm{Fe(s)\ |\ Fe$$^{2+}$$(aq)\ ||\ Ag^+(aq)\ |\ Ag(s)}$$

Question 19

A redox reaction has $$n = 2$$ electrons transferred, $$E^\circ_{cell} = 0.50\ V$$, and occurs at $$25^\circ C. $$What is $$\Delta G^\circ$$ for the reaction? ($$F = 96,500\ \mathrm{C/mol\ e^-})$$

Accepted Answer

$$\Delta G^\circ = -2 	imes 96,500 	imes 0.50 = -96,500\ \mathrm{J}$$

Electrochemistry: Principles, Calculations, and Applications

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