Question

In the following redox reactions, ${NH}_3$ appears either in reactant or product. In which case, equivalent weight of ${NH}_3$ is maximum?

• A. $N_2+3H_2⟶2{NH}_3$
• B. $4{NH}_3+5O_2⟶4NO+6H_{2}O$
• C. $2{NH}_3+2Na⟶4Na{NH}_2+H_2$
• D. Equal in the above all cases

Answer 1

Answer: (C)

$2{NH}_3+2Na⟶4Na{NH}_2+H_2$

As we know, Equivalent weight $=$ Molar weight/change in oxidation.
So, equivalent weight is maximum when change in oxidation state is minimum.
Here,
$N_2+3H_2⟶2{NH}_3$
0 0 -3 +1
$4{NH}_3+5O_2⟶4NO+6H_{2}O$
-3 +2
$2{NH}_3+2Na⟶4Na{NH}_2+H_2$
-3 +1 -3 0
So, change is minimum when equivalent weight will be highest.