The equilibrium constant, KP for the gaseous reaction A⇔2B is related to degree of dissociation α of A and total pressure P as

In the above reaction, moqs at t= 0 , A=1 , 2B = 0

At equilibrium, A=1–α, B= 2α

So, KP=Kn(P/n)∆ng

Here, P= total pressure and n= total mass

Now, K=(nB)2/nA[P/n]2–1

KP= (2α)2/(1–α)[P/1+α]

KP=4α2P/1–α2

Therefore, the correct answer is option (A)4α2P/1-α2.