Problem 88
Use the following \(E^{\circ}\) for the electrode potentials, calculate \(\Delta G^{\circ}\) in \(\mathrm{kJ}\) for the indicated reaction : $$ \begin{aligned} 5 \mathrm{Ce}^{4+}(a q)+\mathrm{Mn}^{2+}(a q)+4 \mathrm{H}_{2} \mathrm{O}(l) & 5 \mathrm{Ce}^{3+}(a q) ; \quad+\mathrm{MnO}_{4}^{-}(a q)+8 \mathrm{H}^{+}(a q) \\ \mathrm{MnO}_{4}^{-}(a q)+8 \mathrm{H}^{+}(a q)+5 e^{-} & \mathrm{Mn}^{2+}(a q)+4 \mathrm{H}_{2} \mathrm{O}(l) ; \quad E^{\circ}=+1.51 \mathrm{~V} \end{aligned} $$ \(\mathrm{Ce}^{4+}(\alpha q)+\mathrm{e}^{-} \longrightarrow \mathrm{Ce}^{3+}(a q) \quad E^{\circ}=+1.61 \mathrm{~V}\) (a) \(-9.65\) (b) \(-24.3\) (c) \(-48.25\) (d) \(-35.2\)
Problem 89
Consider an electrochemical cell in which the following reaction occurs and predict which changes will decrease the cell voltage : $$ \mathrm{Fe}^{2+}(a q)+\mathrm{Ag}^{+}(a q) \longrightarrow \mathrm{Ag}(s)+\mathrm{Fe}^{3+}(a q) $$ (I) decrease the [Ag^ '] (II) increase in \(\left[\mathrm{Fe}^{3+}\right.\) ] (1II) increase the amount of \(\mathrm{Ag}\) (a) I (b) II and III (c) II (d) I and II
Problem 93
\(\mathrm{Co}\left|\mathrm{Co}^{2+}\left(\mathrm{C}_{2}\right) \| \mathrm{Co}^{2+}\left(\mathrm{C}_{1}\right)\right| \mathrm{Co} ;\) for this cell, \(\Delta G\) is negative if : (a) \(\mathrm{C}_{2}>\mathrm{C}_{1}\) (b) \(\mathrm{C}_{1}>\mathrm{C}_{2}\) (c) \(\mathrm{C}_{1}=\mathrm{C}_{2}\) (d) unpredictable
Problem 95
For the electrochemical cell \(\operatorname{Pt}(s) \mid \begin{aligned}&\mathrm{H}_{2}(g)\left|\mathrm{H}^{+}(1 M) \| \mathrm{Cu}^{2+}(1 M)\right| \mathrm{Cu}(s), \text { which one of the } \\\&1 \text { atm }\end{aligned}\) following statements is true ? (a) \(\mathrm{H}_{2}\) liberated at anode and \(\mathrm{Cu}\) is deposite at cathode. (b) \(\mathrm{H}_{2}\) liberated at cathode and \(\mathrm{Cu}\) is deposite at anode. (c) Oxidation occurs at cathode. (d) Reduction occurs at anode.
Problem 99
Calculate the standard voltage that can be obtained from an ethane oxygen fuel cell at \(25^{\circ} \mathrm{C} .\) \(\mathrm{C}_{2} \mathrm{H}_{6}(g)+7 / 2 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(l) ; \quad \Delta G^{\circ}=-1467 \mathrm{~kJ}\) (a) \(+0.91\) (b) \(+0.54\) (c) \(+0.72\) (d) \(+1,08\)
Problem 100
\(\mathrm{I}_{2}(\mathrm{~s}) \mid 1^{-}(0.1 \mathrm{M})\) half cell is connected to a \(\mathrm{H}^{+}(a q)\left|\mathrm{H}_{2}(1 \mathrm{bar})\right| \mathrm{Pt}\) half cell and e.m.f. is found to be \(0.7714 \mathrm{~V}\). If \(E_{\left.\mathrm{I}_{2}\right|^{-}}^{\circ}=0.535 \mathrm{~V}\), find the \(\mathrm{pH}\) of \(\mathrm{H}^{+} \mid \mathrm{H}_{2}\) half-cell. (a) 1 (b) 3 (c) 5 (d) 7
Problem 105
The \(E^{\circ}\) at \(25^{\circ} \mathrm{C}\) for the following reaction at the indicated concentrations is \(1.50 \mathrm{~V}\). Calculate the \(\Delta G\) in \(\mathrm{kJ}\) at \(25^{\circ} \mathrm{C}\) : $$ \operatorname{Cr}(s)+3 \mathrm{Ag}^{+}(a q, 0.1 \mathrm{M}) \longrightarrow \mathrm{Ag}(s)+\mathrm{Cr}^{3+}(a q, 0.1 \mathrm{M}) $$ (a) \(-140.94\) (b) \(-295\) (c) \(-212\) (d) \(-422.83\)
Problem 107
Consider the following standard electrode potentials and calculate the equilibrium constant at \(25^{\circ} \mathrm{C}\) for the indicated disproportionation reaction : $$ \begin{aligned} 3 \mathrm{Mn}^{2+}(a q) & \longrightarrow \mathrm{Mn}(s)+2 \mathrm{Mn}^{3+}(a q) \\ \mathrm{Mn}^{3+}(a q)+e^{-} & \longrightarrow \mathrm{Mn}^{2+}(a q) ; \quad E^{\circ}=1.51 \mathrm{~V} \\ \mathrm{Mn}^{2+}(a q)+2 e^{\circ} \longrightarrow \mathrm{Mn}(s) ; & E^{\circ}=-1.185 \mathrm{~V} \end{aligned} $$ (a) \(1.2 \times 10^{-43}\) (b) \(2.4 \times 10^{-73}\) (c) \(6.3 \times 10^{-92}\) (d) \(1.5 \times 10^{-62}\)
Problem 115
When a lead storage battery is charged it acts as : (a) a fuel cell (b) an electrolytic cell (c) a galvanic cell (d) a concentration cell
Problem 116
The metal that forms a self-protecting film of oxide to prevent corrosion is : (a) Na (b) \(\mathrm{Al}\) (c) Cu (d) Au
