Question

$Cu\left(s\right)+N{O}_3^{-}\left(aq\right)+H^{+}\left(aq\right)\to C{u}^{2+}\left(aq\right)+N{O}_2\left(g\right)+H_{2}O\left(l\right)$
Select the correct statement regarding above reaction.

• A. $Cu\left(s\right)$ is oxidized
• B. $Cu\left(s\right)$ is reduced
• C. $H^{+}\left(aq\right)$ is oxidized
• D. $H^{+}\left(aq\right)$ is reduced
• E. $N{O}_3^{-}\left(aq\right)$ is oxidized

Answer 1

The correct option is A $Cu\left(s\right)$ is oxidized

$Cu$ is oxidized as its oxidation number increases and $N$ is reduced as its oxidation number decreases.
Note: The balancing of the chemical equation is as shown.
The unbalanced chemical equation is $Cu\left(s\right)+N{O}_3^{-}\left(aq\right)+H^{+}\left(aq\right)\to C{u}^{2+}\left(aq\right)+N{O}_2\left(g\right)+H_{2}O\left(l\right)$
$Cu$ and $N$ atoms are balanced.
The oxidation number of $Cu$ increases from 0 to +2. The total increase in the oxidation number is 2.
The oxidation number of $N$ decreases from +5 to +4. The total decrease in oxidation number is 1.
Balance increase in oxidation number with decrease in oxidation number by multiplying the $N$ species with 2.
$Cu\left(s\right)+2N{O}_3^{-}\left(aq\right)+H^{+}\left(aq\right)\to C{u}^{2+}\left(aq\right)+2N{O}_2\left(g\right)+H_{2}O\left(l\right)$
Balance O atoms by adding one water molecule on RHS
$Cu\left(s\right)+2N{O}_3^{-}\left(aq\right)+H^{+}\left(aq\right)\to C{u}^{2+}\left(aq\right)+2N{O}_2\left(g\right)+2H_{2}O\left(l\right)$
Balance H atoms by adding coefficient 4 to proton on LHS
$Cu\left(s\right)+2N{O}_3^{-}\left(aq\right)+4H^{+}\left(aq\right)\to C{u}^{2+}\left(aq\right)+2N{O}_2\left(g\right)+2H_{2}O\left(l\right)$
This is the balanced chemical equation.