17.1 Review of Redox Chemistry

Identify each half-reaction below as either oxidation or reduction.

(a) $\text{Fe}^{3+} + \text{3e}^{−} \rightarrow \text{Fe}$

(b) $\text{Cr} \rightarrow \text{Cr}^{3+} + \text{3e}^{−}$

(c) $\text{MnO}_{4} ^{2−} \rightarrow \text{MnO}_{4} ^{-} + \text{e}^{−}$

(d) $\text{Li}^{+} + \text{e}^{−} \rightarrow \text{Li}$

Assuming each pair of half-reactions below takes place in an acidic solution, write a balanced equation for the overall reaction.

(a) $\text{Ca} \rightarrow \text{Ca}^{2+} + \text{2e}^{−} ,$ $\text{F}_{2} + \text{2e}^{−} \rightarrow \text{2F}^{−}$

(b) $\text{Li} \rightarrow \text{Li}^{+} + \text{e}^{−} ,$ $\text{Cl}_{2} + \text{2e}^{−} \rightarrow \text{2Cl}^{−}$

(c) $\text{Fe} \rightarrow \text{Fe}^{3+} + \text{3e}^{−} ,$ $\text{Br}_{2} + \text{2e}^{-} \rightarrow \text{2Br}^{-}$

(d) $\text{Ag} \rightarrow \text{Ag}^{+} + \text{e}^{−} ,$ $\text{MnO}_{4} ^{-} + \text{4H}^{+} + \text{3e}^{−} \rightarrow \text{MnO}_{2} + \text{2H}_{2} \text{O}$

Identify the oxidant and reductant of each reaction of the previous exercise.

Identify the oxidant and reductant of each reaction of the previous exercise.

Why don’t hydrogen ions appear in equations for half-reactions occurring in basic solution?