Question

What will be the expression of Kp for the given reaction if the total pressure inside the vessel is P and degree of dissociation of the reactant is α? The reaction: N2O4 (g) ⇌ 2NO2

• A. $\frac{4α^2P}{(1+α^2)}$
• B. $\frac{4α^2P}{(1-α^2)}$
• C. $\frac{α^2P}{(1-α^2)}$
• D. $\frac{α^2}{(1-α)}$

Answer 1

Answer: (B)

$\frac{4α^2P}{(1-α^2)}$

Answer 2

Reaction	N2O4 (g) ⇌ 2NO2
Moles at t = 0	1
Moles at equilibrium	1-α

Total moles at **equilibrium **= 1 - α + 2α = 1+α
$p_{N_2 O_4}=\left(\frac{1-a}{1+a}\right) P ;$
$p_{NO_2}=\left(\frac{2a}{1+a}\right)P$
$K_{P}=\frac{p_{NO_2}}{p_{N_2O_4}}=\frac{\left(\frac{2a}{1+a}\right)^{2} p^{2}}{\left(\frac{1-a}{1+a}\right)p}$
$=\frac{4a^{2}p}{1-a^{2}}$