Question 1

Which of the following best describes what occurs at the anode in a galvanic (voltaic) cell?

Accepted Answer

Oxidation occurs and electrons are produced.

Question 2

Given the following half-reactions and standard reduction potentials:

$$\mathrm{Mg$$^{2+}$$ + 2e^- \rightarrow Mg} \quad E^\circ = -2.38\,V$$

$$\mathrm{Cr$$^{3+}$$ + 3e^- \rightarrow Cr} \quad E^\circ = -0.74\,V$$

What is the maximum voltage for a cell constructed from these two half-cells, and what is the overall balanced cell reaction?

Accepted Answer

$$E^\circ_{cell} = 1.64\,V;\ 3Mg + 2Cr$$^{3+}$$ \rightarrow 3Mg$$^{2+}$$ + 2Cr$$

Question 3

Which of the following statements about the standard cell potential ($$E^\circ_{cell}) is $$correct?

Accepted Answer

A positive $$E^\circ_{cell}$$ means the cell reaction is spontaneous.

Question 4

In the electrolysis of molten NaCl, which species is reduced at the cathode?

Accepted Answer

$$\mathrm{Na^+}$$

Question 5

A Daniell cell is constructed with 1.0 M $$\mathrm{Zn$$^{2+}$$}$$ and 1.0 M $$\mathrm{Cu$$^{2+}$$} at 25$$°C. The standard cell potential is $$1.10\,V. $$What is the equilibrium constant $$K$$ for the cell reaction?

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

Accepted Answer

$$K = 1.6 	imes 10$$^{37}$$

Question 6

Which of the following best explains why the reduction of water occurs instead of sodium ion during the electrolysis of aqueous NaCl?

Accepted Answer

The reduction of water is more spontaneous (less negative $$E^\circ) $$than that of sodium ion.

Question 7

A pH meter works by measuring the voltage difference between two electrodes. If the measured cell voltage for the following cell is $$0.211\,V at$$ $$25^\circ C$$, what is the pH of the test solution?

$$\mathrm{Zn (s) \mid Zn$$^{2+}$$ (1.0\,M) \parallel H^+ (test) \mid H_2$ (1\,atm) \mid Pt}$$

$$E^\circ_{cell} = 0.76\,V$$

Accepted Answer

pH = 9.27

Question 8

Which of the following is the correct Nernst equation for a cell at $$25^\circ C$$?

Accepted Answer

$$E_{cell} = E^\circ_{cell} - \dfrac{0.0592}{n} \log Q$$

Question 9

Which of the following is a real-world application of electrolysis?

Accepted Answer

Production of sodium metal from molten NaCl

Question 10

In a lead-acid battery, which of the following reactions occurs at the positive plate during discharge?

Accepted Answer

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

Question 11

Which of the following best describes the relationship between the standard cell potential ($$E^\circ_{cell}) $$and the standard Gibbs free energy change ($$\Delta G^\circ$$)?

Accepted Answer

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

Question 12

Which of the following is the correct shorthand notation for a Daniell cell?

Accepted Answer

$$\mathrm{Zn (s) \mid Zn$$^{2+}$$ (aq) \parallel Cu$$^{2+}$$ (aq) \mid Cu (s)}$$

Question 13

Which of the following is a correct statement about rechargeable batteries such as Ni-Cd or lithium-ion cells?

Accepted Answer

The cell reactions are reversible, allowing the battery to be recharged.

Question 14

During the electrolysis of aqueous NaCl, which products are collected at the cathode and anode, respectively?

Accepted Answer

H$$_2 at $$the cathode, Cl$$_2 at $$the anode

Question 15

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

Accepted Answer

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

Question 16

Which of the following metals would be the best choice for the anode in a battery designed to produce the highest possible voltage, based on standard reduction potentials?

Accepted Answer

Lithium

Question 17

If the concentration of $$\mathrm{Zn$$^{2+}$$} in a $$Daniell cell is decreased to $$1.0 	imes 10$$^{-5}$$\,M$$ while $$\mathrm{Cu$$^{2+}$$} is$$ $$0.100\,M$$, what happens to the cell potential compared to the standard cell potential?

Accepted Answer

The cell potential increases.

Electrochemistry: Redox Reactions, Batteries, and Electrolysis

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