d
\(\quad \quad \quad \quad 2 A B_{2}(g) \rightleftharpoons 2 A B(g)+B_{2}(g) \)

\(\text { Initial moles } \;\; 1 \quad \;\;\;\;\quad 0 \quad \quad \quad \quad 0\)

At equil. \(\quad 2(1-x)\quad \quad 2 x\quad \quad \quad x\)

where, \(x=\) degree of dissociation

Total moles at equilibrium

\(=2-2 x+2 x+x=(2+x)\)

\(\text { So, } p_{A B 2}= \frac{2(1-x) p}{(2+x)}, p_{A B}=\frac{2 x p}{(2+x)}\)

\(p_{B 2}= \frac{x p}{(2+x)}\)

\(K_{p}=\frac{p_{A} s}{\left(p_{A}\right)^{2}\left(P_{B 2}\right)}\)

\(=\frac{\left(\frac{2 r p}{2+p}\right)^{2}\left[\left(\frac{x}{2+x}\right) p\right]}{\left[\left(\frac{2 a-x}{(2+x)}\right) p\right]}\)

\(=\frac{x^{3} p}{(2+x)(1-x)^{2}}\)

\(=\frac{x^{3} p}{2}[\cdots x < < < 1 \text { and } 2]\)

\(x =\left(\frac{2 K p}{p}\right)^{1 / 3}\)

So, \((1-x) \approx ; 1(2+x) \approx 2\)