# Question 9ba07

Oct 18, 2016

$M n {O}_{2} \left(s\right) + 3 A {g}^{+} + 2 {H}_{2} O \left(l\right) \rightarrow M n {O}_{4}^{-} + 3 A g \left(s\right) \downarrow + 4 {H}^{+}$

Are charge and mass balanced?

#### Explanation:

$\text{Oxidation: } M n \left(I V\right) \rightarrow M n \left(V I I\right)$

$M n {O}_{2} \left(s\right) + 2 {H}_{2} O \left(l\right) \rightarrow M n {O}_{4}^{-} + 4 {H}^{+} + 3 {e}^{-}$ $\left(i\right)$ ;E^@=-1.68V

$\text{Reduction: } M n \left(I V\right) \rightarrow M n \left(V I I\right)$

$A {g}^{+} + {e}^{-} \rightarrow A g \left(s\right)$ $\left(i i\right)$ ;E^@=0.80V

$\text{Overall: } 1 \times \left(i\right) + 3 \times \left(i i\right)$,

$M n {O}_{2} \left(s\right) + 3 A {g}^{+} + 2 {H}_{2} O \left(l\right) \rightarrow M n {O}_{4}^{-} + 3 A g \left(s\right) \downarrow + 4 {H}^{+}$
;E^@=-0.78V

I looked up the electrode potentials, and the reaction is NOT feasible. Reduction of $A {g}^{2 +}$ would drive the reaction:

$A {g}^{2 +} + 2 {e}^{-} \rightarrow A g \left(s\right)$ $\left(i i i\right)$ ;E^@=1.99V#