A mixture of Nitrogen and Hydrogen (1:3 mole ratio) is at an initial pressure of 200atm. If 20% of the mixture reacts by the time equilibrium is reached, the equilibrium pressure of the mixture is

The equilibrium reaction for the preparation of ammonia is

$\underset{200 \mathrm{atm}}{{\mathrm{N}}_2+3{\mathrm{H}}_2}\rightleftharpoons \underset{0}{2{\mathrm{NH}}_3}$

Initial(atm): 200         0 

Equilibrium: 200 - x    2x

200-20 atm        

 $2\times 20 \mathrm{atm}$

=180 atm

Therefore, equilibrium pressure of the mixture $\left({\mathrm{N}}_2 \mathrm{and} {\mathrm{H}}_2\right)$is 180 atm.