Justify that the following reactions are redox reactions:
$a$. $CuO_{(s)} + H_{2(g)} \rightarrow Cu_{(s)} + H_2O_{(g)}$
$b$. $Fe_2O_{3(s)} + 3CO_{(g)} \rightarrow 2Fe_{(s)} + 3CO_{2(g)}$
$c$. $4BCl_{3(g)} + 3LiAlH_{4(s)} \rightarrow 2B_2H_{6(g)} + 3LiCl_{(s)} + 3AlCl_{3(s)}$
$d$. $2K_{(s)} + F_{2(g)} \rightarrow 2K^{+}F^{-}_{(s)}$
$e$. $4NH_{3(g)} + 5O_{2(g)} \rightarrow 4NO_{(g)} + 6H_2O_{(g)}$

(N/A) . $CuO_{(s)} + H_{2(g)} \rightarrow Cu_{(s)} + H_2O_{(g)}$
Oxidation numbers: $\mathop{Cu}\limits^{+2} \mathop{O}\limits^{-2}_{(s)} + \mathop{H_2}\limits^0_{(g)}$ $\rightarrow \mathop{Cu}\limits^0_{(s)} + \mathop{H_2}\limits^{+1} \mathop{O}\limits^{-2}_{(g)}$
$Cu$ is reduced ($+2$ to $0$) and $H$ is oxidized ($0$ to $+1$).
$b$. $Fe_2O_{3(s)} + 3CO_{(g)} \rightarrow 2Fe_{(s)} + 3CO_{2(g)}$
Oxidation numbers: $\mathop{Fe_2}\limits^{+3} \mathop{O_3}\limits^{-2}_{(s)} + 3\mathop{C}\limits^{+2} \mathop{O}\limits^{-2}_{(g)}$ $\rightarrow 2\mathop{Fe}\limits^0_{(s)} + 3\mathop{C}\limits^{+4} \mathop{O_2}\limits^{-2}_{(g)}$
$Fe$ is reduced ($+3$ to $0$) and $C$ is oxidized ($+2$ to $+4$).
$c$. $4BCl_{3(g)} + 3LiAlH_{4(s)} \rightarrow 2B_2H_{6(g)} + 3LiCl_{(s)} + 3AlCl_{3(s)}$
Oxidation numbers: $4\mathop{B}\limits^{+3} \mathop{Cl_3}\limits^{-1}_{(g)} + 3\mathop{Li}\limits^{+1} \mathop{Al}\limits^{+3} \mathop{H_4}\limits^{-1}_{(s)}$ $\rightarrow 2\mathop{B_2}\limits^{-3} \mathop{H_6}\limits^{+1}_{(g)} + 3\mathop{Li}\limits^{+1} \mathop{Cl}\limits^{-1}_{(s)} + 3\mathop{Al}\limits^{+3} \mathop{Cl_3}\limits^{-1}_{(s)}$
$B$ is reduced ($+3$ to $-3$) and $H$ is oxidized ($-1$ to $+1$).
$d$. $2K_{(s)} + F_{2(g)} \rightarrow 2K^{+}F^{-}_{(s)}$
Oxidation numbers: $2\mathop{K}\limits^0_{(s)} + \mathop{F_2}\limits^0_{(g)}$ $\rightarrow 2\mathop{K^{+}}\limits^{+1} \mathop{F^{-}}\limits^{-1}_{(s)}$
$K$ is oxidized ($0$ to $+1$) and $F$ is reduced ($0$ to $-1$).
$e$. $4NH_{3(g)} + 5O_{2(g)} \rightarrow 4NO_{(g)} + 6H_2O_{(g)}$
Oxidation numbers: $4\mathop{N}\limits^{-3} \mathop{H_3}\limits^{+1}_{(g)} + 5\mathop{O_2}\limits^0_{(g)}$ $\rightarrow 4\mathop{N}\limits^{+2} \mathop{O}\limits^{-2}_{(g)} + 6\mathop{H_2}\limits^{+1} \mathop{O}\limits^{-2}_{(g)}$
$N$ is oxidized ($-3$ to $+2$) and $O$ is reduced ($0$ to $-2$).