Question

For which one of the following reactions $ K_{p} = K_{c} $ ?

• A. $N_{2}+3H_{2} \rightleftharpoons 2NH_{3} $
• B. $ N_{2}+O_{2}\rightleftharpoons 2NO $
• C. $ PCl_{5}\rightleftharpoons PCl_{3}+Cl_{2} $
• D. $ 2SO_{3}\rightleftharpoons 2SO_{2}+O_{2} $

Answer 1

Answer: (B)

$K_{p}=K_{c}(R T)^{\Delta n_{g}}$
where. $\Delta n_{g}=$ gaseous product - gaseous reactant
when $\Delta n_{g}=0$ then, $K_{p}=K_{c}$
$N_{2}(g)+O_{2}(g) \rightleftharpoons 2 N O(g)$
$ \Delta n_{g}=2-2=0$
$K_{p}=K_{c}(R T)^{0}$
$ \therefore K_{p}=K_{c}$