AB₂ dissociates as :  When the intial pressure of AB₂ is 500 mm Hg, the total equilibrium pressure is 700 mm Hg. Calculate equilibrium constant for the reaction, assuming that the volume of the system remains unchanged.

Initial pressure of AB₂ (g) = 500 mm

Equilibrium pressure = 700 mm

Let 'P' mm of AB₂ decomposed at equilibrium

2 mole of AB₂ gives 1 mole of AB

Pmm of AB₂ gives _____ mm of AB

Pressure of AB at equilibrium = 'P' mm

1 moles of AB₂ gives 1 mole of B

Pmm of AB₂ gives ____ mm of B

Pressure of AB at equilibrium = 'P' mm

Initial pressure	500 mm		____	____
Equilibrium pressure	(500 - P)		P	P

Total pressure at equilibrium = 500 - P + P + P = 500 + P

Given (500 + P) = 700

At equilibrium

K_p = 133.33 mm