6) (15 points) Choose which direction is spontaneous for the following reaction. Calculate \( E^{O} \) for the spontaneous reaction. If you now calculate \( \mathrm{E} \) using the Nernst equation, you find that \( \mathrm{E}=1.18 \mathrm{eV} \). Calculate the concentration of \( \mathrm{Al}^{3+} \) if the concentration of \( \mathrm{Fe}^{2+} \) is \( 2.25 \mathrm{M} \). If you let this battery run at 3.6 amps, how long in minutes would you have to wait to lose 1.3 grams of your anode? \[ \mathrm{Fe}^{2+}+\mathrm{Al}^{\circ} \longleftrightarrow \mathrm{Fe}^{\circ}+\mathrm{Al}^{3+} \]
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The standard reduction potentials for the half-reactions are: Fe2+ + 2e- -> Fe E° = -0.44 V Al3+ + 3e- -> Al E° = -1.66 V The reaction with the more positive E° value will proceed as a reduction in the spontaneous direction. Therefore, Fe2+ will be reduced to Fe Show more…
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Consider a voltaic cell at $25^{\circ} \mathrm{C}$ in which the following reaction takes place. $$ 3 \mathrm{H}_{2} \mathrm{O}_{2}(a q)+6 \mathrm{H}^{+}(a q)+2 \mathrm{Au}(s) \longrightarrow 2 \mathrm{Au}^{3+}(a q)+6 \mathrm{H}_{2} \mathrm{O} $$ (a) Calculate $E^{\circ}$. (b) Write the Nernst equation for the cell. (c) Calculate $E$ when $\left[\mathrm{Au}^{3+}\right]=0.250 \mathrm{M},\left[\mathrm{H}^{+}\right]=1.25 \mathrm{M},\left[\mathrm{H}_{2} \mathrm{O}_{2}\right]=$ $1.50 \mathrm{M}$
Consider a voltaic cell at $25^{\circ} \mathrm{C}$ in which the following reaction takes place. $$ 3 \mathrm{H}_{2} \mathrm{O}_{2}(a q)+6 \mathrm{H}^{+}(a q)+2 \mathrm{Au}(s) \longrightarrow 2 \mathrm{Au}^{3+}(a q)+6 \mathrm{H}_{2} \mathrm{O} $$ (a) Calculate $E^{\circ}$. (b) Write the Nernst equation for the cell. (c) Calculate $E$ when $\left[\mathrm{Au}^{3+}\right]=0.250 \mathrm{M},\left[\mathrm{H}^{+}\right]=1.25 \mathrm{M}$ $\left[\mathrm{H}_{2} \mathrm{O}_{2}\right]=1.50 \mathrm{M}$
56. Consider a voltaic cell in which the following reaction takes place in basic medium at $25^{\circ} \mathrm{C}$. $$ 2 \mathrm{NO}_{3}^{-}(a q)+3 \mathrm{~S}^{2-}(a q)+4 \mathrm{H}_{2} \mathrm{O} \longrightarrow 3 \mathrm{~S}(s)+2 \mathrm{NO}(g)+8 \mathrm{OH}^{-}(a q) $$ (a) Calculate $E^{\circ}$. (b) Write the Nernst equation for the cell voltage $E$. (c) Calculate $E$ under the following conditions: $P_{\mathrm{NO}}=0.994 \mathrm{~atm},$ $\mathrm{pH}=13.7,\left[\mathrm{~S}^{2-}\right]=0.154 \mathrm{M},\left[\mathrm{NO}_{3}^{-}\right]=0.472 \mathrm{M}$
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