How do chromium metal, and Pb^(2+) interact electrochemically?

Sep 9, 2015

Chromium metal is oxidized to $C {r}^{3 +}$, and lead is reduced from $P {b}^{2 +}$ to $P {b}^{0}$. Half equations follow.

Explanation:

Oxidation half equation:

$C r \rightarrow C {r}^{3 +} + 3 {e}^{-} \left(i\right)$

Reduction half equation:

$P b {\left(N {O}_{3}\right)}_{2} + 2 {e}^{-} \rightarrow P {b}^{0} + 2 N {O}_{3}^{-}$ $\left(i i\right)$

Both equations are balanced with respect to mass, and to charge. The overall equation is simply the sum of equations (i) and (ii) such that electrons do not appear in the final reaction: i.e. $2 \times \left(i\right) + 3 \times \left(i i\right) :$

$2 C r + 3 P b {\left(N {O}_{3}\right)}_{2} \rightarrow 2 C {r}^{3 +} + 3 P {b}^{0} + 6 N {O}_{3}^{-}$.

Note that the overall redox equation is balanced with respect to mass and charge, as indeed it must be.