Chemistry and Chemical Reactivity

John C. Kotz, Paul M. Treichel, Gabriela C. Weaver

Chapter 20

Principles of Reactivity: Electron Transfer Reactions - all with Video Answers

Educators

+ 1 more educators

Chapter Questions

Problem 1

Write balanced equations for the following half-reactions. Specify whether each is an oxidation or reduction.
(a) $\operatorname{Cr}(\mathrm{s}) \longrightarrow \mathrm{Cr}^{3+}(\mathrm{aq}) \quad$ (in acid)
(b) $\mathrm{AsH}_{3}(\mathrm{g}) \longrightarrow \mathrm{As}(\mathrm{s}) \quad$ (in acid)
(c) $\mathrm{VO}_{3}^{-}(\mathrm{aq}) \longrightarrow \mathrm{V}^{2+}(\mathrm{aq}) \quad$ (in acid)
(d) $\mathrm{Ag}(\mathrm{s}) \longrightarrow \mathrm{Ag}_{2} \mathrm{O}(\mathrm{s})$ (in base)

Andrew Engley

Andrew Engley

Numerade Educator

Problem 2

Write balanced equations for the following half-reactions. Specify whether each is an oxidation or reduction.
(a) $\mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{aq}) \longrightarrow \mathrm{O}_{2}(\mathrm{g}) \quad$ (in acid)
(b) $\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(\mathrm{aq}) \longrightarrow \mathrm{CO}_{2}(\mathrm{g}) \quad$ (in acid)
(c) $\mathrm{NO}_{3}^{-}(\mathrm{aq}) \longrightarrow \mathrm{NO}(\mathrm{g})$ (in acid)
(d) $\mathrm{MnO}_{4}^{-}(\mathrm{aq}) \longrightarrow \mathrm{MnO}_{2}(\mathrm{s})$ (in base)

Lottie Adams

Numerade Educator

Problem 3

Balance the following redox equations. All occur in acid solution.
(a) $\mathrm{Ag}(\mathrm{s})+\mathrm{NO}_{3}^{-}(\mathrm{aq}) \longrightarrow \mathrm{NO}_{2}(\mathrm{g})+\mathrm{Ag}^{+}(\mathrm{aq})$
(b) $\mathrm{MnO}_{4}^{-}(\mathrm{aq})+\mathrm{HSO}_{3}^{-}(\mathrm{aq}) \longrightarrow$
$\mathrm{Mn}^{2+}(\mathrm{aq})+\mathrm{SO}_{4}^{2-}(\mathrm{aq})$
(c) $\mathrm{Zn}(\mathrm{s})+\mathrm{NO}_{3}^{-}(\mathrm{aq}) \longrightarrow \mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{N}_{2} \mathrm{O}(\mathrm{g})$
(d) $\operatorname{Cr}(\mathrm{s})+\mathrm{NO}_{3}^{-}(\mathrm{aq}) \longrightarrow \mathrm{Cr}^{3+}(\mathrm{aq})+\mathrm{NO}(\mathrm{g})$

Krish Desai

Numerade Educator

Problem 4

Balance the following redox equations. All occur in acid solution.
(a) $\mathrm{Sn}(\mathrm{s})+\mathrm{H}^{+}(\mathrm{aq}) \longrightarrow \mathrm{Sn}^{2+}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})$
(b) $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(\mathrm{aq})+\mathrm{Fe}^{2+}(\mathrm{aq}) \longrightarrow \mathrm{Cr}^{3+}(\mathrm{aq})+\mathrm{Fe}^{3+}(\mathrm{aq})$
(c) $\mathrm{MnO}_{2}(\mathrm{s})+\mathrm{Cl}^{-}(\mathrm{aq}) \longrightarrow \mathrm{Mn}^{2+}(\mathrm{aq})+\mathrm{Cl}_{2}(\mathrm{g})$
(d) $\mathrm{CH}_{2} \mathrm{O}(\mathrm{aq})+\mathrm{Ag}^{+}(\mathrm{aq}) \longrightarrow \mathrm{HCO}_{2} \mathrm{H}(\mathrm{aq})+\mathrm{Ag}(\mathrm{s})$

Shreestika Pradhan

Shreestika Pradhan

Numerade Educator

Problem 5

Balance the following redox equations. All occur in basic solution.
(a) $\mathrm{Al}(\mathrm{s})+\mathrm{OH}^{-}(\mathrm{aq}) \longrightarrow \mathrm{Al}(\mathrm{OH})_{4}^{-}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})$
(b) $\mathrm{CrO}_{4}^{2-}(\mathrm{aq})+\mathrm{SO}_{3}^{2-}(\mathrm{aq}) \longrightarrow$
$\mathrm{Cr}(\mathrm{OH})_{3}(\mathrm{s})+\mathrm{SO}_{4}^{2-}(\mathrm{aq})$
(c) $\mathrm{Zn}(\mathrm{s})+\mathrm{Cu}(\mathrm{OH})_{2}(\mathrm{s}) \longrightarrow\left[\mathrm{Zn}(\mathrm{OH})_{4}\right]^{2-}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})$
(d) $\mathrm{HS}^{-}(\mathrm{aq})+\mathrm{ClO}_{3}^{-}(\mathrm{aq}) \longrightarrow \mathrm{S}(\mathrm{s})+\mathrm{Cl}^{-}(\mathrm{aq})$

Lottie Adams

Numerade Educator

Problem 6

Balance the following redox equations. All occur in basic solution.
(a) $\operatorname{Fe}(\text { OH })_{3}(s)+\operatorname{Cr}(s) \longrightarrow \operatorname{Cr}(\text { OH })_{3}(s)+\operatorname{Fe}(\text { OH })_{2}(s)$
(b) $\mathrm{NiO}_{2}(\mathrm{s})+\mathrm{Zn}(\mathrm{s}) \longrightarrow \mathrm{Ni}(\mathrm{OH})_{2}(\mathrm{s})+\mathrm{Zn}(\mathrm{OH})_{2}(\mathrm{s})$
(c) $\mathrm{Fe}(\mathrm{OH})_{2}(\mathrm{s})+\mathrm{CrO}_{4}^{2-}(\mathrm{aq}) \longrightarrow$
$\mathrm{Fe}(\mathrm{OH})_{3}(\mathrm{s})+\left[\mathrm{Cr}(\mathrm{OH})_{4}\right]^{-}(\mathrm{aq})$
(d) $\mathrm{N}_{2} \mathrm{H}_{4}(\mathrm{aq})+\mathrm{Ag}_{2} \mathrm{O}(\mathrm{s}) \longrightarrow \mathrm{N}_{2}(\mathrm{g})+\mathrm{Ag}(\mathrm{s})$

Shreestika Pradhan

Shreestika Pradhan

Numerade Educator

Problem 7

A voltaic cell is constructed using the reaction of chromium metal and iron(II) ion.
$$2 \mathrm{Cr}(\mathrm{s})+3 \mathrm{Fe}^{2+}(\mathrm{aq}) \longrightarrow 2 \mathrm{Cr}^{3+}(\mathrm{aq})+3 \mathrm{Fe}(\mathrm{s})$$
Complete the following sentences: Electrons in the external circuit flow from the _____ electrode to the _____ electrode. Negative ions move in the salt bridge from the _____ half-cell to the half-cell. The half-reaction at the anode is _____ and that at the cathode is ____.

Nicole Krahulik

Nicole Krahulik

Numerade Educator

Problem 8

voltaic cell is constructed using the reaction $\mathrm{Mg}(\mathrm{s})+2 \mathrm{H}^{+}(\mathrm{aq}) \longrightarrow \mathrm{Mg}^{2+}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})$
(a) Write equations for the oxidation and reduction halfreactions.
(b) Which half-reaction occurs in the anode compartment and which occurs in the cathode compartment?
(c) Complete the following sentences: Electrons in the external circuit flow from the ___ electrode to the ___ electrode. Negative ions move in the salt bridge from the ___ half-cell to the ___ half-cell. The half-reaction at the anode is ___ and that at the cathode is ___.

Shreestika Pradhan

Shreestika Pradhan

Numerade Educator

Problem 9

The half-cells $\mathrm{Fe}^{2+}(\text { aq }) | \mathrm{Fe}(\mathrm{s})$ and $\mathrm{O}_{2}(\mathrm{g}) | \mathrm{H}_{2} \mathrm{O}$ (in acid
solution) are linked to create a voltaic cell.
(a) Write equations for the oxidation and reduction halfreactions and for the overall (cell) reaction.
(b) Which half-reaction occurs in the anode compartment and which occurs in the cathode compartment?
(c) Complete the following sentences: Electrons in the external circuit flow from the ___ electrode to the ___ electrode. Negative ions move in the salt bridge from the ___ half-cell to the ___ half-cell.

Andrew Engley

Numerade Educator

Problem 10

The half-cells $\mathrm{Ag}^{+}(\mathrm{aq}) | \mathrm{Ag}(\mathrm{s})$ and $\mathrm{Cl}_{2}(\mathrm{g}) | \mathrm{Cl}^{-}(\mathrm{aq})$ are
linked to create a voltaic cell.
(a) Write equations for the oxidation and reduction halfreactions and for the overall (cell) reaction.
(b) Which half-reaction occurs in the anode compartment and which occurs in the cathode compartment?
(c) Complete the following sentences: Electrons in the external circuit flow from the ___ electrode to the ___ electrode. Negative ions move in the salt bridge from the ___ half-cell to the ___ half-cell.

Nicholas Mogoi

Numerade Educator

Problem 11

What are the similarities and differences between dry cells, alkaline batteries, and ni-cad batteries?

Krish Desai

Numerade Educator

Problem 12

What reactions occur when a lead storage battery is recharged?

Nicholas Mogoi

Numerade Educator

Problem 13

Calculate the value of $E^{\circ}$ for each of the following reactions. Decide whether each is product-favored in the direction written.
(a) $2 \mathrm{I}^{-}(\mathrm{aq})+\mathrm{Zn}^{2+}(\mathrm{aq}) \longrightarrow \mathrm{I}_{2}(\mathrm{s})+\mathrm{Zn}(\mathrm{s})$
(b) $\mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{Ni}(\mathrm{s}) \longrightarrow \mathrm{Zn}(\mathrm{s})+\mathrm{Ni}^{2+}(\mathrm{aq})$
(c) $2 \mathrm{Cl}^{-}(\mathrm{aq})+\mathrm{Cu}^{2+}(\mathrm{aq}) \longrightarrow \mathrm{Cu}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{g})$
(d) $\mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{Ag}^{+}(\mathrm{aq}) \longrightarrow \mathrm{Fe}^{3+}(\mathrm{aq})+\mathrm{Ag}(\mathrm{s})$

Andrew Engley

Numerade Educator

Problem 14

Calculate the value of $E^{\circ}$ for each of the following reactions. Decide whether each is product-favored in the direction written. [Reaction (d) occurs in basic solution.]
(a) $\operatorname{Br}_{2}(\ell)+\operatorname{Mg}(\mathrm{s}) \longrightarrow \mathrm{Mg}^{2+}(\mathrm{aq})+2 \mathrm{Br}^{-}(\mathrm{aq})$
(b) $\mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{Mg}(\mathrm{s}) \longrightarrow \mathrm{Zn}(\mathrm{s})+\mathrm{Mg}^{2+}(\mathrm{aq})$
(c) $\mathrm{Sn}^{2+}(\mathrm{aq})+2 \mathrm{Ag}^{+}(\mathrm{aq}) \longrightarrow \mathrm{Sn}^{4+}(\mathrm{aq})+2 \mathrm{Ag}(\mathrm{s})$
(d) $2 \mathrm{Zn}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(\ell)+4 \mathrm{OH}^{-}(\mathrm{aq}) \longrightarrow$
$2\left[\mathrm{Zn}(\mathrm{OH})_{4}\right]^{2-}(\mathrm{aq})$

Shreestika Pradhan

Shreestika Pradhan

Numerade Educator

Problem 15

Balance each of the following unbalanced equations, then calculate the standard potential, $E^{\circ},$ and decide whether each is product-favored as written. (All reactions occur in acid solution.)
(a) $\mathrm{Sn}^{2+}(\mathrm{aq})+\mathrm{Ag}(\mathrm{s}) \longrightarrow \mathrm{Sn}(\mathrm{s})+\mathrm{Ag}^{+}(\mathrm{aq})$
(b) $\mathrm{Al}(\mathrm{s})+\mathrm{Sn}^{4+}(\mathrm{aq}) \longrightarrow \mathrm{Sn}^{2+}(\mathrm{aq})+\mathrm{Al}^{3+}(\mathrm{aq})$
(c) $\mathrm{ClO}_{3}^{-}(\mathrm{aq})+\mathrm{Ce}^{3+}(\mathrm{aq}) \longrightarrow \mathrm{Cl}^{-}(\mathrm{aq})+\mathrm{Ce}^{4+}(\mathrm{aq})$
(d) $\mathrm{Cu}(\mathrm{s})+\mathrm{NO}_{3}^{-}(\mathrm{aq}) \longrightarrow \mathrm{Cu}^{2+}(\mathrm{aq})+\mathrm{NO}(\mathrm{g})$

Lottie Adams

Numerade Educator

Problem 16

Balance each of the following unbalanced equations, then calculate the standard potential, $E^{\circ},$ and decide whether each is product-favored as written. (All reactions occur in acid solution.)
(a) $\mathrm{I}_{2}(\mathrm{s})+\mathrm{Br}^{-}(\mathrm{aq}) \longrightarrow \mathrm{I}^{-}(\mathrm{aq})+\mathrm{Br}_{2}(\ell)$
(b) $\mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{Cu}^{2+}(\mathrm{aq}) \longrightarrow \mathrm{Cu}(\mathrm{s})+\mathrm{Fe}^{3+}(\mathrm{aq})$
(c) $\mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(\mathrm{aq}) \longrightarrow \mathrm{Fe}^{3+}(\mathrm{aq})+\mathrm{Cr}^{3+}(\mathrm{aq})$
(d) $\mathrm{MnO}_{4}^{-}(\mathrm{aq})+\mathrm{HNO}_{2}(\mathrm{aq}) \longrightarrow \mathrm{Mn}^{2+}(\mathrm{aq})+\mathrm{NO}_{3}^{-}(\mathrm{aq})$

Lottie Adams

Numerade Educator

Problem 17

Consider the following half-reactions:
(TABLE CANNOT COPY)
(a) Based on $E^{\circ}$ values, which metal is the most easily oxidized?
(b) Which metals on this list are capable of reducing $\mathrm{Fe}^{2+}(\mathrm{aq})$ to $\mathrm{Fe} ?$
(c) Write a balanced chemical equation for the reaction of $\mathrm{Fe}^{2+}(\mathrm{aq})$ with $\mathrm{Sn}(\mathrm{s}) .$ Is this reaction product-favored or reactant-favored?
(d) Write a balanced chemical equation for the reaction of $\mathrm{Zn}^{2+}(\mathrm{aq})$ with $\mathrm{Sn}(\mathrm{s}) .$ Is this reaction product-favored or reactant-favored?

Andrew Engley

Numerade Educator

Problem 18

Consider the following half-reactions:
(TABLE CANNOT COPY)
(a) Choosing from among the reactants in these halfreactions, identify the strongest and weakest oxidizing agents.
(b) Which of the oxidizing agents listed is (are) capable of oxidizing $\mathrm{Br}^{-}(\text {aq })$ to $\mathrm{BrO}_{3}^{-}(\text {aq })$ (in acid solution)?
(c) Write a balanced chemical equation for the reaction of $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(\mathrm{aq})$ with $\mathrm{SO}_{2}(\mathrm{g})$ in acid solution. Is this reac-
tion product-favored or reactant-favored?
(d) Write a balanced chemical equation for the reaction of $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}$ (aq) with $\mathrm{Mn}^{2+}$ (aq). Is this reaction productfavored or reactant-favored?

Lottie Adams

Numerade Educator

Problem 19

Which of the following elements is the best reducing agent?
(a) Cu
(b) $\mathrm{Zn}$
(c) $\mathrm{Fe}$
(d) $\mathrm{Ag}$
(e) $\mathrm{Cr}$

Andrew Engley

Numerade Educator

Problem 20

From the following list, identify those elements that are easier to oxidize than $\mathrm{H}_{2}(\mathrm{g})$
(a) $\mathrm{Cu}$
(b) $\mathrm{Zn}$
(c) $\mathrm{Fe}$
(d) $\mathrm{Ag}$
(e) $\mathrm{Cr}$

Nicholas Mogoi

Numerade Educator

Problem 21

Which of the following ions is most easily reduced?
(a) $\mathrm{Cu}^{2+}(\mathrm{aq})$
(b) $\mathrm{Zn}^{2+}(\mathrm{aq})$
(c) $\mathrm{Fe}^{2+}(\mathrm{aq})$
(d) $\mathrm{Ag}^{+}(\mathrm{aq})$
(e) $\mathrm{Al}^{3+}(\mathrm{aq})$

Andrew Engley

Numerade Educator

Problem 22

From the following list, identify the ions that are more easily reduced than $\mathrm{H}^{+}(\mathrm{aq})$
(a) $\mathrm{Cu}^{2+}(\mathrm{aq})$
(b) $\mathrm{Zn}^{2+}(\mathrm{aq})$
(c) $\mathrm{Fe}^{2+}(\mathrm{aq})$
(d) $\mathrm{Ag}^{+}(\mathrm{aq})$
(e) $\mathrm{Al}^{3+}(\mathrm{aq})$

Nicholas Mogoi

Numerade Educator

Problem 23

(a) Which halogen is most easily reduced: $\mathrm{F}_{2}, \mathrm{Cl}_{2}, \mathrm{Br}_{2}$ or $\mathrm{I}_{2}$ in acidic solution.
(b) Identify the halogens that are better oxidizing agents than $\mathrm{MnO}_{2}(\mathrm{s})$ in acidic solution.

Andrew Engley

Numerade Educator

Problem 24

(a) Which ion is most easily oxidized to the elemental halogen: $\mathrm{F}^{-}, \mathrm{Cl}^{-}, \mathrm{Br}^{-},$ or $\mathrm{I}^{-}$ in acidic solution.
(b) Identify the halide ions that are more easily oxidized than $\mathrm{H}_{2} \mathrm{O}(\ell)$ in acidic solution.

Lottie Adams

Numerade Educator

Problem 25

Calculate the voltage delivered by a voltaic cell using the following reaction if all dissolved species are $2.5 \times 10^{-2} \mathrm{M}$
$\mathrm{Zn}(\mathrm{s})+2 \mathrm{H}_{2} \mathrm{O}(\ell)+2 \mathrm{OH}^{-}(\mathrm{aq}) \longrightarrow$
$\left[\mathrm{Zn}(\mathrm{OH})_{4}\right]^{2-}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})$

Andrew Engley

Numerade Educator

Problem 26

Calculate the potential developed by a voltaic cell using the following reaction if all dissolved species are $0.015 \mathrm{M}$ $2 \mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{aq})+2 \mathrm{H}^{+}(\mathrm{aq}) \longrightarrow$
$2 \mathrm{Fe}^{3+}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\ell)$

Lottie Adams

Numerade Educator

Problem 27

One half-cell in a voltaic cell is constructed from a silver wire dipped into a $0.25 \mathrm{M}$ solution of $\mathrm{AgNO}_{3} .$ The other half-cell consists of a zinc electrode in a $0.010 \mathrm{M}$ solution of $\mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2} .$ Calculate the cell potential.

Andrew Engley

Numerade Educator

Problem 28

One half-cell in a voltaic cell is constructed from a copper wire dipped into a $4.8 \times 10^{-3} \mathrm{M}$ solution of $\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}$ The other half-cell consists of a zinc electrode in a $0.40 \mathrm{M}$ solution of $\mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2} .$ Calculate the cell potential.

Lottie Adams

Numerade Educator

Problem 29

One half-cell in a voltaic cell is constructed from a silver wire dipped into a AgNO $_{3}$ solution of unknown concentration. The other half-cell consists of a zinc electrode in a 1.0 M solution of Zn (NO $_{3}$ ) . A voltage of 1.48 V is measured for this cell. Use this information to calculate the concentration of $\mathrm{Ag}^{+}(\mathrm{aq})$

Andrew Engley

Numerade Educator

Problem 30

One half-cell in a voltaic cell is constructed from an iron wire dipped into an $\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}$ solution of unknown concentration. The other half-cell is a standard hydrogen electrode. A voltage of $0.49 \mathrm{V}$ is measured for this cell. Use this information to calculate the concentration of $\mathrm{Fe}^{2+}(\mathrm{aq})$.

Lottie Adams

Numerade Educator

Problem 31

Calculate $\Delta G^{\circ}$ and the equilibrium constant for the following reactions.
(a) $2 \mathrm{Fe}^{3+}(\mathrm{aq})+2 \mathrm{I}^{-}(\mathrm{aq}) \longrightarrow 2 \mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{I}_{2}(\mathrm{aq})$
(b) $\mathrm{I}_{2}(\mathrm{aq})+2 \mathrm{Br}^{-}(\mathrm{aq}) \longrightarrow 2 \mathrm{I}^{-}(\mathrm{aq})+\mathrm{Br}_{2}(\mathrm{aq})$

Andrew Engley

Numerade Educator

Problem 32

Calculate $\Delta G^{\circ}$ and the equilibrium constant for the following reactions.
(a) $\mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{Ni}(\mathrm{s}) \longrightarrow \mathrm{Zn}(\mathrm{s})+\mathrm{Ni}^{2+}(\mathrm{aq})$
(b) $\mathrm{Cu}(\mathrm{s})+2 \mathrm{Ag}^{+}(\mathrm{aq}) \longrightarrow \mathrm{Cu}^{2+}(\mathrm{aq})+2 \mathrm{Ag}(\mathrm{s})$

Lottie Adams

Numerade Educator

Problem 33

Use standard reduction potentials (Appendix M) for the half-reactions $\mathrm{AgBr}(\mathrm{s})+\mathrm{e}^{-} \longrightarrow \mathrm{Ag}(\mathrm{s})+\mathrm{Br}^{-}(\mathrm{aq})$ and $\mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{e}^{-} \longrightarrow \mathrm{Ag}(\mathrm{s})$ to calculate the value of $K_{\mathrm{sp}}$ for
AgBr.

Lottie Adams

Numerade Educator

Problem 34

Use the standard reduction potentials (Appendix M) for the half-reactions $\mathrm{Hg}_{2} \mathrm{Cl}_{2}(\mathrm{s})+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{Hg}(\ell)+$ $2 \mathrm{Cl}^{-}(\mathrm{aq})$ and $\mathrm{Hg}_{2}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{Hg}(\ell)$ to calculate the value of $K_{\mathrm{sp}}$ for $\mathrm{Hg}_{2} \mathrm{Cl}_{2}$

Lottie Adams

Numerade Educator

Problem 35

Use the standard reduction potentials (Appendix M) for the half-reactions $\left[\mathrm{AuCl}_{4}\right]^{-}(\mathrm{aq})+3 \mathrm{e}^{-} \longrightarrow \mathrm{Au}(\mathrm{s})+$ $4 \mathrm{Cl}^{-}(\mathrm{aq})$ and $\mathrm{Au}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \longrightarrow \mathrm{Au}(\mathrm{s})$ to calculate the value of $K_{\text {formation }}$ for the complex ion $\left[\mathrm{AuCl}_{4}\right]^{-}(\mathrm{aq})$

Lottie Adams

Numerade Educator

Problem 36

Use the standard reduction potentials (Appendix M) for the half-reactions $\left[\mathrm{Zn}(\mathrm{OH})_{4}\right]^{2-}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Zn}(\mathrm{s})+$ $4 \mathrm{OH}^{-}(\mathrm{aq})$ and $\mathrm{Zn}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Zn}(\mathrm{s})$ to calculate the value of $K_{\text {formation }}$ for the complex ion $\left[\mathrm{Zn}(\mathrm{OH})_{4}\right]^{2-}$

Lottie Adams

Numerade Educator

Problem 37

Iron(II) ion undergoes a disproportionation reaction to give $\mathrm{Fe}(\mathrm{s})$ and the iron(III) ion. That is, iron(II) ion is both oxidized and reduced within the same reaction.
$$3 \mathrm{Fe}^{2+}(\mathrm{aq}) \longrightarrow \mathrm{Fe}(\mathrm{s})+2 \mathrm{Fe}^{3+}(\mathrm{aq})$$
(a) What two half-reactions make up the disproportionation reaction?
(b) Use the values of the standard reduction potentials for the two half-reactions in part (a) to determine whether this disproportionation reaction is productfavored.
(c) What is the equilibrium constant for this reaction?

Andrew Engley

Numerade Educator

Problem 38

A Copper(I) ion disproportionates to copper metal and copper(II) ion. (See Study Question 37 .)
$$2 \mathrm{Cu}^{+}(\mathrm{aq}) \longrightarrow \mathrm{Cu}(\mathrm{s})+\mathrm{Cu}^{2+}(\mathrm{aq})$$
(a) What two half-reactions make up the disproportionation reaction?
(b) Use values of the standard reduction potentials for the two half-reactions in part (a) to determine whether this disproportionation reaction is product-favored.
(c) What is the equilibrium constant for this reaction?

Lottie Adams

Numerade Educator

Problem 39

Diagram the apparatus used to electrolyze molten NaCl. Identify the anode and the cathode. Trace the movement of electrons through the external circuit and the movement of ions in the electrolysis cell.

Krish Desai

Numerade Educator

Problem 40

Diagram the apparatus used to electrolyze aqueous $\mathrm{CuCl}_{2}$ Identify the reaction products, the anode, and the cathode. Trace the movement of electrons through the external circuit and the movement of ions in the electrolysis cell.

Lottie Adams

Numerade Educator

Problem 41

Which product, $\mathrm{O}_{2}$ or $\mathrm{F}_{2}$, is more likely to form at the anode in the electrolysis of an aqueous solution of KF? Explain your reasoning.

Andrew Engley

Numerade Educator

Problem 42

Which product, Ca or $\mathrm{H}_{2}$, is more likely to form at the cathode in the electrolysis of $\mathrm{CaCl}_{2} ?$ Explain your reasoning.

Nicholas Mogoi

Numerade Educator

Problem 43

An aqueous solution of KBr is placed in a beaker with two inert platinum electrodes. When the cell is attached to an external source of electrical energy, electrolysis occurs.
(a) Hydrogen gas and hydroxide ion form at the cathode. Write an equation for the half-reaction that occurs at this electrode.
(b) Bromine is the primary product at the anode. Write an equation for its formation.

Andrew Engley

Numerade Educator

Problem 44

An aqueous solution of $\mathrm{Na}_{2} \mathrm{S}$ is placed in a beaker with two inert platinum electrodes. When the cell is attached to an external battery, electrolysis occurs.
(a) Hydrogen gas and hydroxide ion form at the cathode. Write an equation for the half-reaction that occurs at this electrode.
(b) Sulfur is the primary product at the anode. Write an equation for its formation.

Arun Bana

Numerade Educator

Problem 45

In the electrolysis of a solution containing $\mathrm{Ni}^{2+}$ (aq), metallic $\mathrm{Ni}(\mathrm{s})$ deposits on the cathode. Using a current of 0.150 A for 12.2 min, what mass of nickel will form?

Andrew Engley

Numerade Educator

Problem 46

In the electrolysis of a solution containing $\mathrm{Ag}^{+}(\mathrm{aq})$ metallic Ag(s) deposits on the cathode. Using a current of
1.12 A for 2.40 $\mathrm{h}$, what mass of silver forms?

Nicholas Mogoi

Numerade Educator

Problem 47

Electrolysis of a solution of $\mathrm{CuSO}_{4}(\mathrm{aq})$ to give copper metal is carried out using a current of 0.66 A. How long should electrolysis continue to produce $0.50 \mathrm{g}$ of copper?

Andrew Engley

Numerade Educator

Problem 48

Electrolysis of a solution of $\mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})$ to give zinc metal is carried out using a current of 2.12 A. How long should electrolysis continue to prepare $2.5 \mathrm{g}$ of zinc?

Ted Gray

Numerade Educator

Problem 49

A voltaic cell can be built using the reaction between Al metal and $\mathrm{O}_{2}$ from the air. If the Al anode of this cell consists of $84 \mathrm{g}$ of aluminum, how many hours can the cell produce 1.0 A of electricity, assuming an unlimited supply of $\mathrm{O}_{2} ?$

Andrew Engley

Numerade Educator

Problem 50

Assume the specifications of a Ni-Cd voltaic cell include delivery of 0.25 A of current for $1.00 \mathrm{h}$. What is the minimum mass of the cadmium that must be used to make the anode in this cell?

Nicholas Mogoi

Numerade Educator

Problem 51

Write balanced equations for the following half-reactions.
(a) $\mathrm{UO}_{2}^{+}(\mathrm{aq}) \longrightarrow \mathrm{U}^{4+}(\mathrm{aq}) \quad$ (acid solution)
(b) $\mathrm{ClO}_{3}^{-}(\mathrm{aq}) \longrightarrow \mathrm{Cl}^{-}(\mathrm{aq}) \quad$ (acid solution)
(c) $\mathrm{N}_{2} \mathrm{H}_{4}(\mathrm{aq}) \longrightarrow \mathrm{N}_{2}(\mathrm{g})$ (basic solution)
(d) $\mathrm{ClO}^{-}(\mathrm{aq}) \longrightarrow \mathrm{Cl}^{-}(\mathrm{aq}) \quad$ (basic solution)

Andrew Engley

Numerade Educator

Problem 52

Balance the following equations.
(a) $\mathrm{Zn}(\mathrm{s})+\mathrm{VO}^{2+}(\mathrm{aq}) \longrightarrow$
$$\mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{V}^{3+}(\mathrm{aq}) \text { (acid solution) }$$
(b) $\mathrm{Zn}(\mathrm{s})+\mathrm{VO}_{3}^{-}(\mathrm{aq}) \longrightarrow$
$$\mathrm{V}^{2+}(\mathrm{aq})+\mathrm{Zn}^{2+}(\mathrm{aq}) \text { (acid solution) }$$
(c) $\mathrm{Zn}(\mathrm{s})+\mathrm{ClO}^{-}(\mathrm{aq}) \longrightarrow$
$$\mathrm{Zn}(\mathrm{OH})_{2}(\mathrm{s})+\mathrm{Cl}^{-}(\mathrm{aq}) \text { (basic solution) }$$
(d) $\mathrm{ClO}^{-}(\mathrm{aq})+\left[\mathrm{Cr}(\mathrm{OH})_{4}\right]^{-}(\mathrm{aq}) \longrightarrow$
$$\mathrm{Cl}^{-}(\mathrm{aq})+\mathrm{CrO}_{4}^{2-}(\mathrm{aq}) \text { (basic solution) }$$

Lottie Adams

Numerade Educator

Problem 53

Magnesium metal is oxidized and silver ions are reduced in a voltaic cell using $\mathrm{Mg}^{2+}(\mathrm{aq}, 1 \mathrm{M}) | \mathrm{Mg}$ and $\mathrm{Ag}^{+}(\mathrm{aq}, 1 \mathrm{M}) |$ Ag half-cells.
(IMAGE NOT COPY)
(a) Label each part of the cell.
(b) Write equations for the half-reactions occurring at the anode and the cathode, and write an equation for the net reaction in the cell.
(c) Trace the movement of electrons in the external circuit. Assuming the salt bridge contains $\mathrm{NaNO}_{3},$ trace the movement of the $\mathrm{Na}^{+}$ and $\mathrm{NO}_{3}^{-}$ ions in the salt bridge that occurs when a voltaic cell produces current. Why is a salt bridge required in a cell?

Andrew Engley

Numerade Educator

Problem 54

You want to set up a series of voltaic cells with specific cell voltages. $A Z n^{2+}(a q, 1 M) | Z n(s)$ half-cell is in one compartment. Identify several half-cells that you could use so that the cell voltage will be close to (a) $1.1 \mathrm{V}$ and (b) $0.5 \mathrm{V}$ Consider cells in which zinc can be either the cathode or the anode.

Lottie Adams

Numerade Educator

Problem 55

You want to set up a series of voltaic cells with specific cell voltages. The $\mathrm{Ag}^{+}(\mathrm{aq}, 1 \mathrm{M}) | \mathrm{Ag}(\mathrm{s})$ half-cell is one of the compartments. Identify several half-cells that you could use so that the cell voltage will be close to (a) $1.7 \mathrm{V}$ and (b) $0.5 \mathrm{V} .$ Consider cells in which silver can be either the cathode or the anode.

Lottie Adams

Numerade Educator

Problem 56

Which of the following reactions are product-favored?
(a) $\mathrm{Zn}(\mathrm{s})+\mathrm{I}_{2}(\mathrm{s}) \longrightarrow \mathrm{Zn}^{2+}(\mathrm{aq})+2 \mathrm{I}^{-}(\mathrm{aq})$
(b) $2 \mathrm{Cl}^{-}(\mathrm{aq})+\mathrm{I}_{2}(\mathrm{s}) \longrightarrow \mathrm{Cl}_{2}(\mathrm{g})+2 \mathrm{I}^{-}(\mathrm{aq})$
(c) $2 \mathrm{Na}^{+}(\mathrm{aq})+2 \mathrm{Cl}^{-}(\mathrm{aq}) \longrightarrow 2 \mathrm{Na}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{g})$
(d) $2 \mathrm{K}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\ell) \longrightarrow$ $2 \mathrm{K}^{+}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})+2 \mathrm{OH}^{-}(\mathrm{aq})$

Lottie Adams

Numerade Educator

Problem 57

In the table of standard reduction potentials, locate the half-reactions for the reductions of the following metal ions to the metal: $\operatorname{Sn}^{2+}(\mathrm{aq}), \mathrm{Au}^{+}(\mathrm{aq}), \mathrm{Zn}^{2+}(\mathrm{aq}), \mathrm{Co}^{2+}(\mathrm{aq})$ $\mathrm{Ag}^{+}(\mathrm{aq}), \mathrm{Cu}^{2+}(\mathrm{aq}) .$ Among the metal ions and metals that
make up these half-reactions:
(a) Which metal ion is the weakest oxidizing agent?
(b) Which metal ion is the strongest oxidizing agent?
(c) Which metal is the strongest reducing agent?
(d) Which metal is the weakest reducing agent?
(e) Will $\operatorname{Sn}(\mathrm{s})$ reduce $\mathrm{Cu}^{2+}(\mathrm{aq})$ to $\mathrm{Cu}(\mathrm{s}) ?$
(f) Will Ag(s) reduce $\operatorname{Co}^{2+}(\text { aq) to } \operatorname{Co}(\mathrm{s}) ?$
(g) Which metal ions on the list can be reduced by $\operatorname{Sn}(\mathrm{s}) ?$
(h) What metals can be oxidized by $\mathrm{Ag}^{+}(\mathrm{aq}) ?$

Krish Desai

Numerade Educator

Problem 58

A In the table of standard reduction potentials, locate the half-reactions for the reductions of the following nonmetals: $\mathrm{F}_{2}, \mathrm{Cl}_{2}, \mathrm{Br}_{2}, \mathrm{I}_{2}$ (reduction to halide ions), and $\mathrm{O}_{2}$ S, Se (reduction to $\mathrm{H}_{2} \mathrm{X}$ in aqueous acid). Among the elements, ions, and compounds that make up these halfreactions:
(a) Which element is the weakest oxidizing agent?
(b) Which element is the weakest reducing agent?
(c) Which of the elements listed is (are) capable oxidizing $\mathrm{H}_{2} \mathrm{O}$ to $\mathrm{O}_{2} ?$
(d) Which of these elements listed is (are) capable of oxidizing $\mathrm{H}_{2} \mathrm{S}$ to $\mathrm{S} ?$
(e) Is $O_{2}$ capable of oxidizing $I^{-}$ to $I_{2}$, in acid solution?
(f) Is S capable of oxidizing $I^{-}$ to $I_{2} ?$
(g) Is the reaction $\mathrm{H}_{2} \mathrm{S}(\mathrm{aq})+\mathrm{Se}(\mathrm{s}) \longrightarrow \mathrm{H}_{2} \mathrm{Se}(\mathrm{aq})+\mathrm{S}(\mathrm{s})$ product-favored?
(h) Is the reaction $\mathrm{H}_{2} \mathrm{S}(\mathrm{aq})+\mathrm{I}_{2}(\mathrm{s}) \longrightarrow 2 \mathrm{H}^{+}(\mathrm{aq})+$ $2 \mathrm{I}^{-}(\mathrm{aq})+\mathrm{S}(\mathrm{s})$ product-favored?

Lottie Adams

Numerade Educator

Problem 59

Four voltaic cells are set up. In each, one half-cell contains a standard hydrogen electrode. The second halfcell is one of the following: $\mathrm{Cr}^{3+}(\mathrm{aq}, 1.0 \mathrm{M}) | \mathrm{Cr}(\mathrm{s})$ $\mathrm{Fe}^{2+}(\mathrm{aq}, 1.0 \mathrm{M})\left|\mathrm{Fe}(\mathrm{s}), \mathrm{Cu}^{2+}(\mathrm{aq}, 1.0 \mathrm{M})\right| \mathrm{Cu}(\mathrm{s}),$ or $\mathrm{Mg}^{2+}(\mathrm{aq}, 1.0 \mathrm{M}) | \mathrm{Mg}(\mathrm{s})$
(a) In which of the voltaic cells does the hydrogen electrode serve as the cathode?
(b) Which voltaic cell produces the highest voltage? Which produces the lowest voltage?

Andrew Engley

Numerade Educator

Problem 60

The following half-cells are available: $\mathrm{Ag}^{+}(\mathrm{aq}, 1.0 \mathrm{M})$ $\mathrm{Ag}(\mathrm{s}), \mathrm{Zn}^{2+}(\mathrm{aq}, 1.0 \mathrm{M})\left|\mathrm{Zn}(\mathrm{s}), \mathrm{Cu}^{2+}(\mathrm{aq}, 1.0 \mathrm{M})\right| \mathrm{Cu}(\mathrm{s})$ and $\mathrm{Co}^{2+}(\mathrm{aq}, 1.0 \mathrm{M}) | \mathrm{Co}(\mathrm{s}) .$ Linking any two half-cells
makes a voltaic cell. Given four different half-cells, six voltaic cells are possible. These are labeled, for simplicity, Ag-Zn, Ag-Cu, Ag-Co, Zn-Cu, Zn-Co, and Cu-Co.
(a) In which of the voltaic cells does the copper electrode serve as the cathode? In which of the voltaic cells does the cobalt electrode serve as the anode?
(b) Which combination of half-cells generates the highest voltage? Which combination generates the lowest voltage?

Lottie Adams

Numerade Educator

Problem 61

The reaction occurring in the cell in which $\mathrm{Al}_{2} \mathrm{O}_{3}$ and aluminum salts are electrolyzed is $\mathrm{Al}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \longrightarrow$ $\mathrm{Al}(\mathrm{s}) .$ If the electrolysis cell operates at $5.0 \mathrm{V}$ and $1.0 \mathrm{X}$ $10^{5} \mathrm{A},$ what mass of aluminum metal can be produced in a 24-h day?

Lottie Adams

Numerade Educator

Problem 62

A potential of $+0.146 \mathrm{V}$ is recorded (under standard conditions) for a voltaic cell constructed using the following half-reactions: Anode: $\mathrm{Ag}(\mathrm{s}) \longrightarrow \mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{e}^{-}$
Cathode: $\mathrm{Ag}_{2} \mathrm{SO}_{4}(\mathrm{s})+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{Ag}(\mathrm{s})+\mathrm{SO}_{4}^{2-}(\mathrm{aq})$
(a) What is the standard reduction potential for the cathode reaction?
(b) Calculate the solubility product, $K_{\mathrm{sp}},$ for $\mathrm{Ag}_{2} \mathrm{SO}_{4}$

Lottie Adams

Numerade Educator

Problem 63

A A potential of $0.142 \mathrm{V}$ is recorded (under standard conditions) for a voltaic cell constructed using the following half reactions:
Cathode: $\mathrm{Pb}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Pb}(\mathrm{s})$
Anode: $\operatorname{PbCl}_{2}(\mathrm{s})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Pb}(\mathrm{s})+2 \mathrm{Cl}^{-}(\mathrm{aq})$ Net: $\mathrm{Pb}^{2+}(\mathrm{aq})+2 \mathrm{Cl}^{-}(\mathrm{aq}) \longrightarrow \mathrm{PbCl}_{2}(\mathrm{s})$
(a) What is the standard reduction potential for the anode reaction?
(b) Estimate the solubility product, $K_{s p},$ for $\mathrm{PbCl}_{2}$

Lottie Adams

Numerade Educator

Problem 64

The standard voltage, $E^{\circ},$ for the reaction of $\mathrm{Zn}(\mathrm{s})$ and $\mathrm{Cl}_{2}(\mathrm{g})$ is $+2.12 \mathrm{V}$. What is the standard free energy change, $\overline{\Delta G}^{\circ},$ for the reaction?

Lottie Adams

Numerade Educator

Problem 65

The standard potential for the reaction of $\mathrm{Mg}(\mathrm{s})$ with $\mathrm{I}_{2}(\mathrm{s})$ is $+2.91 \mathrm{V} .$ What is the standard free energy change, $\Delta G^{\circ}$ for the reaction?

Lottie Adams

Numerade Educator

Problem 66

An electrolysis cell for aluminum production operates at $5.0 \mathrm{V}$ and a current of $1.0 \times 10^{5} \mathrm{A}$. Calculate the number of kilowatt-hours of energy required to produce 1 metric ton $\left(1.0 \times 10^{3} \mathrm{kg}\right)$ of aluminum. $(1 \mathrm{kWh}=$ $3.6 \times 10^{6} \mathrm{J}$ and $1 \mathrm{J}=1 \mathrm{C} \cdot \mathrm{V} .$

Lottie Adams

Numerade Educator

Problem 67

A Electrolysis of molten $\mathrm{NaCl}$ is done in cells operating at $7.0 \mathrm{V}$ and $4.0 \times 10^{4} \mathrm{A} .$ What mass of $\mathrm{Na}(\mathrm{s})$ and $\mathrm{Cl}_{2}(\mathrm{g}) \mathrm{can}$ be produced in one day in such a cell? What is the energy consumption in kilowatt-hours? ( $1 \mathrm{kWh}=3.6 \times 10^{6} \mathrm{J}$ and $1 \mathrm{J}=1 \mathrm{C} \cdot \mathrm{V} \cdot \mathrm{J}$.

Andrew Engley

Numerade Educator

Problem 68

A current of $0.0100 \mathrm{A}$ is passed through a solution of rhodium sulfate, causing reduction of the metal ion to the metal. After $3.00 \mathrm{h}, 0.038 \mathrm{g}$ of Rhas been deposited. What is the charge on the rhodium ion, $R h^{n+} ?$ What is the formula for rhodium sulfate?

Lottie Adams

Numerade Educator

Problem 69

A current of $0.44 \mathrm{A}$ is passed through a solution of ruthenium nitrate causing reduction of the metal ion to the metal. After $25.0 \mathrm{min}, 0.345 \mathrm{g}$ of Ru has been deposited. What is the charge on the ruthenium ion, $\mathrm{Ru}^{n+} ?$ What is the formula for ruthenium nitrate?

Andrew Engley

Numerade Educator

Problem 70

The total charge that can be delivered by a large dry cell battery before its voltage drops too low is usually about
35 amp-hours. (One amp-hour is the charge that passes through a circuit when $1 \text { A flows for } 1 \text { h. })$ What mass of Zn is consumed when 35 amp-hours is drawn from the cell?

Lottie Adams

Numerade Educator

Problem 71

Chlorine gas is obtained commercially by electrolysis of brine (a concentrated aqueous solution of $\mathrm{NaCl}$ ). If the electrolysis cells operate at $4.6 \mathrm{V}$ and $3.0 \times 10^{5} \mathrm{A},$ what mass of chlorine can be produced in a 24 -h day?

Lottie Adams

Numerade Educator

Problem 72

An old method of measuring the current flowing in a circuit was to use a "silver coulometer." The current passed first through a solution of $\mathrm{Ag}^{+}(\mathrm{aq})$ and then into another solution containing an electroactive species. The amount of silver metal deposited at the cathode was weighed. From the mass of silver, the number of atoms of silver was calculated. since the reduction of a silver ion requires one electron, this value equalled the number of electrons passing through the circuit. If the time was noted, the average current could be calculated. If, in such an experiment, $0.052 \mathrm{g}$ of $\mathrm{Ag}$ is deposited during $450 \mathrm{s}$, what was the current flowing in the circuit?

Lottie Adams

Numerade Educator

Problem 73

A "silver coulometer" (Study Question 72) was used in the past to measure the current flowing in an electrochemical cell. Suppose you found that the current flowing through an electrolysis cell deposited $0.089 \mathrm{g}$ of $\mathrm{Ag}$ metal at the cathode after exactly 10 min. If this same current then passed through a cell containing gold(III) ion in the form of $\left(\mathrm{AuCl}_{4}\right)^{-}$, how much gold was deposited at the cathode in that electrolysis cell?

Lottie Adams

Numerade Educator

Problem 74

A Write balanced equations for the following reduction half-reactions involving organic compounds.
(a) $\mathrm{HCO}_{2} \mathrm{H} \longrightarrow \mathrm{CH}_{2} \mathrm{O} \quad$ (acid solution)
(b) $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H} \longrightarrow \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{3} \quad$ (acid solution)
(c) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO} \longrightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH} \quad$ (acid solution)
(d) $\mathrm{CH}_{3} \mathrm{OH} \longrightarrow \mathrm{CH}_{4} \quad$ (acid solution)

Lottie Adams

Numerade Educator

Problem 75

A Balance the following equations involving organic compounds.
(a) $\mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CHO}(\mathrm{aq}) \longrightarrow$
$\mathrm{Ag}(\mathrm{s})+\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq}) \quad$ (acid solution)
(b) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}+\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(\mathrm{aq}) \longrightarrow$
$\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq})+\mathrm{Cr}^{3+}(\mathrm{aq}) \quad$ (acid solution)

Krish Desai

Numerade Educator

Problem 76

A voltaic cell is constructed in which one half-cell consists of a silver wire in an aqueous solution of AgNO $_{3} .$ The other half-cell consists of an inert platinum wire in an aqueous solution containing $\mathrm{Fe}^{2+}(\mathrm{aq})$ and $\mathrm{Fe}^{3+}(\mathrm{aq})$
(a) Calculate the voltage of the cell, assuming standard conditions.
(b) Write the net ionic equation for the reaction occurring in the cell.
(c) In this voltaic cell, which electrode is the anode and which is the cathode?
(d) If $\left[\mathrm{Ag}^{+}\right]$ is $0.10 \mathrm{M},$ and $\left[\mathrm{Fe}^{2+}\right]$ and $\left[\mathrm{Fe}^{3+}\right]$ are both 1.0 M, what is the cell voltage? Is the net cell reaction still that used in part (a)? If not, what is the net reaction under the new conditions?

Lottie Adams

Numerade Educator

Problem 77

An expensive but lighter alternative to the lead storage battery is the silver-zinc battery.
$$\mathrm{Ag}_{2} \mathrm{O}(\mathrm{s})+\mathrm{Zn}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\ell) \longrightarrow \mathrm{Zn}(\mathrm{OH})_{2}(\mathrm{s})+2 \mathrm{Ag}(\mathrm{s})$$
The electrolyte is $40 \%$ KOH, and silver-silver oxide electrodes are separated from zinc-zinc hydroxide electrodes by a plastic sheet that is permeable to hydroxide ion. Under normal operating conditions, the battery has a potential of $1.59 \mathrm{V}$
(a) How much energy can be produced per gram of reactants in the silver-zinc battery? Assume the battery produces a current of $0.10 \mathrm{A}$
(b) How much energy can be produced per gram of reactants in the standard lead storage battery? Assume the battery produces a current of $0.10 \mathrm{A}$ at $2.0 \mathrm{V}$
(c) Which battery (silver-zinc or lead storage) produces the greater energy per gram of reactants?

Lottie Adams

Numerade Educator

Problem 78

The specifications for a lead storage battery include delivery of a steady 1.5 A of current for 15 h.
(a) What is the minimum mass of lead that will be used in the anode?
(b) What mass of $\mathrm{PbO}_{2}$ must be used in the cathode?
(c) Assume that the volume of the battery is $0.50 \mathrm{L}$. What is the minimum molarity of $\mathrm{H}_{2} \mathrm{SO}_{4}$ necessary?

Nicholas Mogoi

Numerade Educator

Problem 79

Fluorinated organic compounds are important commercially, as they are used as herbicides, flame retardants, and fire-extinguishing agents, among other things. A reaction such as
$$\mathrm{CH}_{3} \mathrm{SO}_{2} \mathrm{F}+3 \mathrm{HF} \longrightarrow \mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{F}+3 \mathrm{H}_{2}$$
is carried out electrochemically in liquid HF as the solvent.
(a) If you electrolyze $150 \mathrm{g}$ of $\mathrm{CH}_{3} \mathrm{SO}_{2} \mathrm{F},$ what mass of $\mathrm{HF}$ is required and what mass of each product can be isolated?
(b) Is $\mathrm{H}_{2}$ produced at the anode or the cathode of the electrolysis cell?
(c) A typical electrolysis cell operates at $8.0 \mathrm{V}$ and $250 \mathrm{A}$ How many kilowatt-hours of energy does one such cell consume in $24 \mathrm{h} ?$

Lottie Adams

Numerade Educator

Problem 80

A The free energy change for a reaction, $\Delta G_{\mathrm{rxm}}^{\circ},$ is the maximum energy that can be extracted from the process, whereas $\Delta H_{\mathrm{rxn}}^{\circ}$ is the total chemical potential energy change. The efficiency of a fuel cell is the ratio of these two quantities.
$$\text { Efficiency }=\frac{\Delta G_{\text {rxn }}^{\circ}}{\Delta H_{\text {rxn }}^{o}} \times 100 \%$$
Consider the hydrogen-oxygen fuel cell where the net reaction is
$$\mathrm{H}_{2}(\mathrm{g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{g}) \longrightarrow \mathrm{H}_{2} \mathrm{O}(\ell)$$
(a) Calculate the efficiency of the fuel cell under standard conditions.
(b) Calculate the efficiency of the fuel cell if the product is water vapor instead of liquid water.
(c) Does the efficiency depend on the state of the reaction product? Why or why not?

Lottie Adams

Numerade Educator

Problem 81

Consider an electrochemical cell based on the halfreactions $\mathrm{Ni}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Ni}(\mathrm{s})$ and $\mathrm{Cd}^{2+}(\mathrm{aq})+$ $2 \mathrm{e}^{-} \longrightarrow \mathrm{Cd}(\mathrm{s})$
(a) Diagram the cell and label each of the components (including the anode, cathode, and salt bridge).
(b) Use the equations for the half-reactions to write a balanced, net ionic equation for the overall cell reaction.
(c) What is the polarity of each electrode?
(d) What is the value of $E_{\text {cell }}^{\circ}$
(e) In which direction do electrons flow in the external circuit?
(f) Assume that a salt bridge containing NaNO $_{3}$ connects the two half-cells. In which direction do the $\mathrm{Na}^{+}$ (aq) ions move? In which direction do the $\mathrm{NO}_{3}^{-}$ (aq) ions move?
(g) Calculate the equilibrium constant for the reaction.
(h) If the concentration of $\mathrm{Cd}^{2+}$ is reduced to $0.010 \mathrm{M}$ and $\left[\mathrm{Ni}^{2+}\right]=1.0 \mathrm{M},$ what is the value of $E_{\text {ccll }} ?$ Is the net reaction still the reaction given in part (b)?
(i) If $0.050 \mathrm{A}$ is drawn from the battery, how long can it last if you begin with 1.0 L of each of the solutions, and each was initially $1.0 \mathrm{M}$ in dissolved species? Each electrode weighs $50.0 \mathrm{g}$ in the beginning.

Lottie Adams

Numerade Educator

Problem 82

(a) Is it easier to reduce water in acid or base? To evaluate this, consider the half-reaction
$$\begin{array}{c}
2 \mathrm{H}_{2} \mathrm{O}(\ell)+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{OH}^{-}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g}) \\
E^{\circ}=-0.83 \mathrm{V}
\end{array}$$
(b) What is the reduction potential for water for solutions at $p H=7$ (neutral) and $p H=1$ (acid)? Comment on the value of $E^{\circ}$ at $\mathrm{pH}=1$

Lottie Adams

Numerade Educator

Problem 83

A solution of KI is added dropwise to a pale blue solution of $\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2} .$ The solution changes to a brown color and a precipitate forms. In contrast, no change is observed if solutions of KCl and KBr are added to aqueous $\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2} .$ Consult the table of standard reduction potentials to explain the dissimilar results seen with the different halides. Write an equation for the reaction that occurs when solutions of KI and $\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}$ are mixed.

Lottie Adams

Numerade Educator

Problem 84

Four metals, $A, B, C,$ and $D,$ exhibit the following properties:
(a) Only A and C react with 1.0 M hydrochloric acid to give $\mathrm{H}_{2}(\mathrm{g})$
(b) When $\mathrm{C}$ is added to solutions of the ions of the other metals, metallic $\mathbf{B}, \mathbf{D},$ and $\mathbf{A}$ are formed.
(c) Metal D reduces $B^{n+}$ to give metallic $B$ and $D^{n+}$ Based on this information, arrange the four metals in order of increasing ability to act as reducing agents.

Lottie Adams

Numerade Educator

Problem 85

A hydrogen-oxygen fuel cell operates on the simple reaction
$$\mathbf{H}_{2}(\mathrm{g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{g}) \longrightarrow \mathrm{H}_{2} \mathrm{O}(\ell)$$
If the cell is designed to produce 1.5 A of current, and if the hydrogen is contained in a 1.0 -L tank at $200 .$ atm pressure at $25^{\circ} \mathrm{C},$ how long can the fuel cell operate before the hydrogen runs out? (Assume there is an unlimited supply of $\left.\mathbf{O}_{2 \cdot}\right)$

Lottie Adams

Numerade Educator

Problem 86

living organisms derive energy from the oxidation of food, typified by glucose.
$$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{aq})+6 \mathrm{O}_{2}(\mathrm{g}) \longrightarrow 6 \mathrm{CO}_{2}(\mathrm{g})+6 \mathrm{H}_{2} \mathrm{O}(\ell)$$
Electrons in this redox process are transferred from glucose to oxygen in a series of at least 25 steps. It is instructive to calculate the total daily current flow in a typical organism and the rate of energy expenditure (power). (See T.P. Chirpich: Journal of Chemical Education, Vol. 52 , p. $99,1975 .)$
(a) The molar enthalpy of combustion of glucose is $-2800 \mathrm{kJ} .$ If you are on a typical daily diet of $2400 \mathrm{Cal}$ (kilocalories), what amount of glucose (in moles) must be consumed in a day if glucose is the only source of energy? What amount of $\mathrm{O}_{2}$ must be consumed in the oxidation process?
(b) How many moles of electrons must be supplied to reduce the amount of $\mathrm{O}_{2}$ calculated in part (a)?
(c) Based on the answer in part (b), calculate the current flowing, per second, in your body from the combustion of glucose.
(d) If the average standard potential in the electron transport chain is $1.0 \mathrm{V},$ what is the rate of energy expenditure in watts?

Lottie Adams

Numerade Educator

Problem 87

See the General ChemistryNow CD-ROM or website Screen $20.7 .$ Using the reduction potential table in the simulation on this screen, answer these questions:
(a) What species can be reduced by $\mathrm{Cu}(\mathrm{s})$ ?
(b) What metals can be oxidized by $\mathrm{Cd}^{2+} ?$

Lottie Adams

Numerade Educator