For gaseous phase process A+B⇌C+D , initially 1 mol each of A & B and 2 mole each of C & D are present. If 2.5 mole each of C & D are present at equilibrium, Kc is

A   +   B   ⇌   C   +   D          1           1              2          2         x          x              x          x_ (1−x)  (1−x)  (2+x)  (2+x)     0.5        0.5          2.5         2.5   Given   2+x=2.5                   ⇒x=0.5          Kc=2.5×2.50.5×0.5=25