Question 1

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

Accepted Answer

Oxidation occurs and electrons are released into the external circuit.

Question 2

Given the following redox reaction: $$\mathrm{Zn(s) + Cu$$^{2+}$$(aq) \rightarrow Zn$$^{2+}$$(aq) + Cu(s)}$$, which species is the oxidizing agent?

Accepted Answer

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

Question 3

What is the standard cell potential ($$E^\circ_{cell}) $$for a galvanic cell constructed from the following half-reactions at 25°C?

$$\mathrm{Zn$$^{2+}$$(aq) + 2e^- \rightarrow Zn(s)}$$ $$E^\circ = -0.76\ V$$
$$\mathrm{Cu$$^{2+}$$(aq) + 2e^- \rightarrow Cu(s)}$$ $$E^\circ = +0.34\ V$$

Accepted Answer

$$E^\circ_{cell} = +1.10\ V$$

Question 4

Which of the following is the correct balanced half-reaction for the reduction of permanganate ion ($$\mathrm{$$MnO_4$$^-}) to$$ $$\mathrm{Mn$$^{2+}$$} in $$acidic solution?

Accepted Answer

$$\mathrm{$$MnO_4$$^-} + 8H^+ + 5e^- \rightarrow Mn$$^{2+}$$ + 4H_2O$$

Question 5

A voltaic cell is constructed with the following cell notation:
$$\mathrm{Zn(s) | Zn$$^{2+}$$(aq) || Cu$$^{2+}$$(aq) | Cu(s)}$$
Which direction do electrons flow in the external circuit?

Accepted Answer

From zinc to copper

Question 6

Using the Nernst equation, which of the following changes will increase the cell potential ($$E_{cell}) $$for a galvanic cell?

$$E_{cell} = E^\circ_{cell} - \frac{RT}{nF} \ln Q$$

Accepted Answer

Decreasing the value of $$Q by $$increasing reactant concentration

Question 7

For the reaction $$\mathrm{4Ag(s) + O_2$(g) + 4H^+(aq) \rightarrow 4Ag^+(aq) + 2H_2O(l)}$$, if $$E^\circ_{cell} = 0.43\ V at 25$$°C, what is the standard free energy change ($$\Delta G^\circ$$)?

Use $$F = 96,485\ \mathrm{C/mol}.$$

Accepted Answer

$$\Delta G^\circ = -166,000\ \mathrm{J}$$

Question 8

Which of the following best explains why a salt bridge is necessary in a voltaic cell?

Accepted Answer

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

Question 9

Consider the following reaction in acidic solution:
$$\mathrm{$$MnO_4$$^-} + 5Fe$$^{2+}$$ + 8H^+ \rightarrow Mn$$^{2+}$$ + 5Fe$$^{3+}$$ + 4H_2O$$
How many electrons are transferred in the balanced equation?

Accepted Answer

25

Question 10

Which of the following is the correct relationship between the equilibrium constant $$K$$ and the standard cell potential $$E^\circ_{cell}$$?

Accepted Answer

$$E^\circ_{cell} = \frac{RT}{nF} \ln K$$

Question 11

A battery is constructed using the following half-cells:
$$\mathrm{Al$$^{3+}$$(aq) + 3e^- \rightarrow Al(s)}$$ $$E^\circ = -1.66\ V$$
$$\mathrm{Fe$$^{2+}$$(aq) + 2e^- \rightarrow Fe(s)}$$ $$E^\circ = -0.44\ V$$
What is the standard cell potential ($$E^\circ_{cell}) $$for the cell: $$\mathrm{Al(s) | Al$$^{3+}$$(aq) || Fe$$^{2+}$$(aq) | Fe(s)}$$?

Accepted Answer

$$E^\circ_{cell} = +1.22\ V ($$after balancing electrons)

Question 12

Which of the following best describes the change in color observed when a strip of zinc is placed in a solution of copper(II) sulfate?

Accepted Answer

The blue color fades as copper(II) ions are reduced to copper metal.

Question 13

In the reaction $$\mathrm{Cd(s) + $$NiO_2$$(s) + 2H_2O(l) \rightarrow Cd(OH)_2(s) + Ni(OH)_2(s)}$$, which element is oxidized?

Accepted Answer

Cadmium

Question 14

A voltaic cell operates at 25°C with $$[Zn$$^{2+}$$] = 0.10\ M$$ and $$[Cu$$^{2+}$$] = 1.0\ M. $$Given $$E^\circ_{cell} = 1.10\ V$$, what is the cell potential ($$E_{cell}$$)?

Use $$E_{cell} = E^\circ_{cell} - \frac{0.0592}{2} \log \frac{[Zn$$^{2+}$$]}{[Cu$$^{2+}$$]}$$

Accepted Answer

$$E_{cell} = 1.07\ V$$

Question 15

Which of the following is true about the sign of $$\Delta G$$ and $$E_{cell}$$ for a spontaneous electrochemical reaction?

Accepted Answer

$$\Delta G is $$negative and $$E_{cell} is $$positive

Question 16

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

Accepted Answer

It prevents the buildup of charge by allowing ions to migrate between half-cells.

Question 17

If the equilibrium constant $$K$$ for a redox reaction is very large, what can be inferred about the standard cell potential $$E^\circ_{cell}$$?

Accepted Answer

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

Electrochemistry: Redox Reactions, Galvanic Cells, and Cell Potentials

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