Question

Justify that the following reactions are redox reactions.

• A. $CuO\left(s\right)+H_2\left(g\right)\to Cu\left(s\right)+H_{2}O\left(g\right)$
• B. ${Fe}_2{O}_3\left(s\right)+3CO\left(g\right)\to 2Fe\left(s\right)+3{CO}_2\left(g\right)$
• C. $4{BCl}_3\left(g\right)+3Li{AlH}_4\left(s\right)\to 2B_2{H}_6\left(s\right)+3LiCl\left(s\right)+3{AlCl}_3\left(s\right)$
• D. $2K\left(s\right)+F_2\left(g\right)\to {2K}^{+}{F}^{-}\left(s\right)$

Answer 1

The correct option is D $2K\left(s\right)+F_2\left(g\right)\to {2K}^{+}{F}^{-}\left(s\right)$

$\left(A\right)$ $\stackrel{+2}{Cu}O\left(s\right)+{\stackrel{0}{H}}_2\left(g\right)⟶\stackrel{0}{Cu}\left(s\right)+{\stackrel{+1}{H}}_{2}O\left(g\right)$

Here, reduction of $\stackrel{+2}{Cu}O$ to $\stackrel{0}{Cu}$ and oxidation of ${\stackrel{0}{H}}_2$ to ${\stackrel{+1}{H}}_{2}O$ takes place. Therefore, it is a redox reaction.

$\left(B\right)$ ${\stackrel{+3}{Fe}}_2{O}_3\left(s\right)+3\stackrel{+2}{CO}\left(g\right)⟶2\stackrel{0}{Fe}\left(s\right)+3{\stackrel{+4}{CO}}_2\left(g\right)$

Here, reduction of ${\stackrel{+3}{Fe}}_2{O}_3$ to $\stackrel{0}{Fe}$ and oxidation of $\stackrel{+2}{CO}$ takes place. Therefore, it is a redox reaction.

$\left(C\right)$ $4\stackrel{+3}{B}{Cl}_3\left(g\right)+3Li\stackrel{+3}{AI}{H}_4\left(s\right)⟶3{\stackrel{+3}{B}}_2{H}_6\left(s\right)+3LiCl\left(s\right)+3\stackrel{+3}{AI}{Cl}_3\left(s\right)$

Here, no change of oxidation states take place. Therefore, it is not a redox reaction.

$\left(D\right)$ $2\stackrel{0}{K}\left(s\right)+{\stackrel{0}{F}}_2\left(g\right)⟶2K^{+}{F}^{-}\left(s\right)$

Here, $\stackrel{0}{K}$ is oxidized to $K^{+1}$ and ${\stackrel{0}{F}}_2$ is reduced to $F^{-1}$. So, it is a redox reaction.