Question

Use the table of standard reduction potentials (Table 11.1) to pick a reagent that is capable of each of the following reduction (under standard conditions in acidic solution).

a.reduces$C{u}^{2+}$to$Cu$but does not reduce$C{u}^{2+}$to$C{u}^{+}$.

b. reduces$B{r}_2$to$B{r}^{-}$but does not reduce$I_2$to$I^{-}$.

Short answer

a. Some of the reagent that can reduce

$C{u}^{2+}\to Cu \text{but} \text{not} C{u}^{2+} are Hg, Ag, H_2{S}_2{O}_3$

b. Some of the reagents that reduce $B{r}_2$$B{r}^{-}$to but does not reduce$I_2$ to $I^{-}$are

$V{O}^{2+}, AuC{I}_4^{-}, Au, NO, H{g}_2^{2+}$

Step-by-step solution

Explanation of reduction 

The reduction as,

$$\begin{gathered} C{u}^{2+}+2e^{-}\to Cu \\ {E}^0=0.34V\backslash \mathrm{hfill} \\ C{u}^{+}+e^{-}\to C{u}^{+} \\ {E}^0=0.16V \end{gathered}$$

The reagents that can reduce$C{u}^{2+}\to Cu \text{but} \text{not} C{u}^{2+} are Hg, Ag, H_2{S}_2{O}_3$

Explanation of the reduction 

The reduction as,

$$\begin{gathered} B{r}_2+2e^{-}\to 2B{r}^{-} \\ {E}^0=1.09V \\ {I}_2+2e^{-}\to 2I^{-} \\ {E}^0=0.54V \\ V{O}^{2+},AuC \end{gathered}$$

The reagents that reduce $B{r}_2$to $B{r}^{-}$but does not reduce $I_2$to $I^{-}$are:

$V{O}^{2+}, AuC{I}_4^{-}, Au, NO, H{g}_2^{2+}$