Question 1

Which of the following statements best describes a redox reaction?

Accepted Answer

A reaction characterized by the transfer of electrons from one reactant to another.

Question 2

In the reaction $$\mathrm{Zn(s) + Cu$$^{2+}$$(aq) \rightarrow Zn$$^{2+}$$(aq) + Cu(s)}$$, which species is oxidized and which is reduced?

Accepted Answer

Zn is oxidized; Cu$$^{2+} is $$reduced.

Question 3

Which rule is used to assign the oxidation number of an atom in a free element?

Accepted Answer

Rule #1: The oxidation number for an atom in a free element is zero.

Question 4

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

Accepted Answer

It prevents the build-up of charge by allowing ions to move between compartments.

Question 5

In a voltaic cell, which electrode is the site of oxidation?

Accepted Answer

Anode

Question 6

Given the half-reactions: $$\mathrm{Cu$$^{2+}$$(aq) + 2e^- \rightarrow Cu(s)}$$ ($$E^\circ = 0.34\,\mathrm{V}) $$and $$\mathrm{Zn(s) \rightarrow Zn$$^{2+}$$(aq) + 2e^-}$$ ($$E^\circ = -0.76\,\mathrm{V}$$), what is the standard cell potential for the overall reaction?

Accepted Answer

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

Question 7

Which of the following reactions will occur spontaneously according to the activity series?

Accepted Answer

$$\mathrm{Li(s) + Au^+(aq) \rightarrow Li^+(aq) + Au(s)}$$

Question 8

What is the relationship between Gibbs free energy ($$\Delta G) $$and cell potential ($$E_{cell}$$)?

Accepted Answer

$$\Delta G = -nFE_{cell}$$

Question 9

Which statement is true about standard reduction potentials ($$E^\circ$$)?

Accepted Answer

A more positive $$E^\circ$$ means the half-reaction is more likely to occur as a reduction.

Question 10

A student sets up a voltaic cell using the reaction $$\mathrm{2Ag^+(aq) + Ni(s) \rightarrow 2Ag(s) + Ni$$^{2+}$$(aq)}. $$Given $$E^\circ_{Ag^+/Ag} = 0.80\,\mathrm{V}$$ and $$E^\circ_{Ni$$^{2+}$$/Ni} = -0.20\,\mathrm{V}$$, what is the standard cell potential?

Accepted Answer

$$E^\circ_{cell} = 0.80\,\mathrm{V} - (-0.20\,\mathrm{V}) = 1.00\,\mathrm{V}$$

Question 11

Which of the following best describes the process occurring at the cathode in a lithium-ion battery during discharge?

Accepted Answer

Lithium ions are reduced and electrons are gained.

Question 12

If the cell potential ($$E_{cell}) $$for a redox reaction is negative under standard conditions, what does this indicate about the reaction?

Accepted Answer

The reaction is nonspontaneous as written.

Question 13

Which of the following is true about the flow of ions in a salt bridge in a voltaic cell?

Accepted Answer

Cations move toward the cathode and anions move toward the anode.

Question 14

Which of the following is the correct Nernst equation for calculating cell potential under nonstandard conditions?

Accepted Answer

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

Question 15

A lead-acid battery consists of multiple cells connected in series. If each cell has a standard cell potential of $$2.02\,\mathrm{V}$$, what is the total voltage for a battery with 6 cells?

Accepted Answer

$$12.12\,\mathrm{V}$$

Question 16

Which of the following best explains why lithium-ion batteries are widely used in portable electronics?

Accepted Answer

Lithium-ion batteries have high energy density and are rechargeable.

Question 17

Which of the following is the strongest oxidizing agent according to the standard reduction potential table?

Accepted Answer

F$$_2(g)$$

Question 18

A student mixes Mg(s) with CuSO$$_4(aq). $$Using the activity series, predict the outcome.

Accepted Answer

Mg will displace Cu$$^{2+}$$, forming MgSO$$_4(aq) $$and Cu(s).

Electrochemistry: Redox Reactions, Electrochemical Cells, and Cell Potentials

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