Problem 2
What oxidation state change does each metal undergo in the following reactions or half-reactions? (a) \(\left[\mathrm{Cr}_{2} \mathrm{O}_{7}\right]^{2-}+14 \mathrm{H}^{+}+6 \mathrm{e}^{-}-2 \mathrm{Cr}^{3+}+7 \mathrm{H}_{2} \mathrm{O}\) (b) \(2 \mathrm{K}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{KOH}+\mathrm{H}_{2}\) (c) \(\mathrm{Fe}_{2} \mathrm{O}_{3}+2 \mathrm{Al} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{Fe}+\mathrm{Al}_{2} \mathrm{O}_{3}\) (d) \(\left[\mathrm{MnO}_{4}\right]^{-}+2 \mathrm{H}_{2} \mathrm{O}+3 \mathrm{e}^{-}-\mathrm{MnO}_{2}+4[\mathrm{OH}]^{-}\)
Problem 3
Which of the following reactions are redox reactions? In those that are, identify the oxidation and reduction processes. (a) \(\mathrm{N}_{2}+3 \mathrm{Mg} \stackrel{\Delta}{\longrightarrow} \mathrm{Mg}_{3} \mathrm{N}_{2}\) (b) \(\mathrm{N}_{2}+\mathrm{O}_{2} \rightarrow 2 \mathrm{NO}\) (c) \(2 \mathrm{NO}_{2} \rightarrow \mathrm{N}_{2} \mathrm{O}_{4}\) (d) \(\mathrm{SbF}_{3}+\mathrm{F}_{2} \rightarrow \mathrm{SbF}_{5}\) (e) \(6 \mathrm{HCl}+\mathrm{As}_{2} \mathrm{O}_{3} \rightarrow 2 \mathrm{AsCl}_{3}+3 \mathrm{H}_{2} \mathrm{O}\) (f) \(2 \mathrm{CO}+\mathrm{O}_{2} \rightarrow 2 \mathrm{CO}_{2}\) \((\mathrm{g}) \mathrm{MnO}_{2}+4 \mathrm{HCl}--\mathrm{MnCl}_{2}+\mathrm{Cl}_{2}+2 \mathrm{H}_{2} \mathrm{O}\) (h) \(\left[\mathrm{Cr}_{2} \mathrm{O}_{7}\right]^{2-}+2[\mathrm{OH}]^{-} \rightleftharpoons 2\left[\mathrm{CrO}_{4}\right]^{2-}+\mathrm{H}_{2} \mathrm{O}\)
Problem 7
Consider the half-reaction: \\[ \begin{array}{r} {\left[\mathrm{MnO}_{4}\right]^{-}(\mathrm{aq})+8 \mathrm{H}^{+}(\mathrm{aq})+5 \mathrm{e}^{-} \rightleftharpoons \mathrm{Mn}^{2+}(\mathrm{aq})+4 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})} \\ E^{\mathrm{o}}=+1.51 \mathrm{V} \end{array} \\] If the ratio of concentrations of \(\left[\mathrm{MnO}_{4}\right]^{-}: \mathrm{Mn}^{2+}\) is 100: 1 determine \(E\) at \(\mathrm{pH}\) values of \((\mathrm{a}) 0.5 ;(\mathrm{b}) 2.0 ;\) and \((\mathrm{c}) 3.5\) \((T=298 \mathrm{K}) .\) Over this pH range, how does the ability of permanganate(VII) (when being reduced to \(\mathrm{Mn}^{2+}\) ) to oxidize aqueous chloride, bromide or iodide ions change?
Problem 11
Given that \(K_{\mathrm{sp}}\) for \(\mathrm{AgI}\) is \(8.51 \times 10^{-17},\) and \(E_{\mathrm{Ag}^{+} / \mathrm{Ag}}^{\circ}=+0.80 \mathrm{V},\) calculate \(E^{\circ}\) for the reduction step: \(\mathrm{AgI}(\mathrm{s})+\mathrm{e}^{-} \rightleftharpoons \mathrm{Ag}(\mathrm{s})+\mathrm{I}^{-}(\mathrm{aq})\) and hence confirm the statement in Section 8.3 that reduction of silver(I) when in the form of solid AgI is thermodynamically less favourable than reduction of AgCl.
Problem 13
Calculate the overall formation constant for \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\) given that the overall formation constant for \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}\) is \(\approx 10^{32}\), and that: \\[ \begin{array}{ll} \mathrm{Fe}^{3+}(\mathrm{aq})+\mathrm{e}^{-} \rightleftharpoons \mathrm{Fe}^{2+}(\mathrm{aq}) & E^{\mathrm{o}}=+0.77 \mathrm{V} \\ {\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}(\mathrm{aq})+\mathrm{e}^{-} \rightleftharpoons\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}(\mathrm{aq})} & E^{\mathrm{o}}=+0.36 \mathrm{V} \end{array} \\]
Problem 15
Determine \(\Delta G^{0}(298 \mathrm{K})\) for the reaction: \\[ 2 \mathrm{CuCl}(\mathrm{s}) \rightleftharpoons \mathrm{Cu}^{2+}(\mathrm{aq})+2 \mathrm{Cl}^{-}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s}) \\] given the following data: \\[ \begin{array}{ll} 2 \mathrm{Cu}^{+}(\mathrm{aq}) \rightleftharpoons \mathrm{Cu}^{2+}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s}) & K=1.81 \times 10^{6} \\\ \mathrm{CuCl}(\mathrm{s}) \rightleftharpoons \mathrm{Cu}^{+}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq}) & K_{\mathrm{sp}}=1.72 \times 10^{-7} \end{array} \\] What does the value of \(\Delta G^{0}\) tell you about the tendency of precipitated CuCl to disproportionate?
Problem 31
In each of the following reactions, relate starting materials and products by the processes of reduction, oxidation, disproportionation or no redox change. In some reactions, more than one process is taking place. \((\mathrm{a})\left[\mathrm{HCO}_{3}\right]^{-}+[\mathrm{OH}]^{-}-\left[\mathrm{CO}_{3}\right]^{2-}+\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{Au}+\mathrm{HNO}_{3}+4 \mathrm{HCl}-\mathrm{HAuCl}_{4}+\mathrm{NO}+2 \mathrm{H}_{2} \mathrm{O}\) (c) \(2 \mathrm{VOCl}_{2}-\mathrm{VOCl}_{3}+\mathrm{VOCl}\) (d) \(\mathrm{SO}_{2}+4 \mathrm{H}^{+}+4 \mathrm{Fe}^{2+}-\mathrm{S}+4 \mathrm{Fe}^{3+}+2 \mathrm{H}_{2} \mathrm{O}\) (e) \(2 \mathrm{CrO}_{2} \mathrm{Cl}_{2}+3 \mathrm{H}_{2} \mathrm{O} \rightarrow\left[\mathrm{Cr}_{2} \mathrm{O}_{7}\right]^{2-}+4 \mathrm{Cl}^{-}+6 \mathrm{H}^{+}\) \((\mathrm{f})\left[\mathrm{IO}_{4}\right]^{-}+2 \mathrm{I}^{-}+\mathrm{H}_{2} \mathrm{O} \rightarrow\left[\mathrm{IO}_{3}\right]^{-}+\mathrm{I}_{2}+2[\mathrm{OH}]^{-}\) \((\mathrm{g}) 2 \mathrm{KCl}+\mathrm{SnCl}_{4} \rightarrow \mathrm{K}_{2}\left[\mathrm{SnCl}_{6}\right]\) (h) \(2 \mathrm{NO}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{HNO}_{2}+\mathrm{HNO}_{3}\)
