Question

The equilibrium constant for the reaction,
$H_2\left(g\right)+I_2\left(g\right)\rightleftharpoons 2HI\left(g\right)$ is $50$ at $500K$. In presence of suitable catalyst, equilibrium is attained four times faster. The equilibrium constant of the reaction at $500K$ in the presence of catalyst should be:

• A. 200
• B. $4\times {10}^4$
• C. 50
• D. 83.6

Answer 1

The correct option is C 50

Catalyst shortens the time taken to reach equilibrium without changing equilibrium position. So when a catalyst is present, the equilibrium is achieved faster but its magnitude remains unaffected. Thus the value of the equilibrium constant in presence of a catalyst is the same as in absence of catalyst. i.e. , 50.

Theory:

Note :- Equilibrium constant changes only with change in temperature, or when we change the stochiometry of the reaction.

A catalyst changes the rate of forward and backward reactions equally and does not affect the value of the equilibrium constant.
Changes in concentration, pressure, temperature,inert gases may affect the equilibrium, favoring either forward or backward reaction but not the equilibrium constant.
And $K_{eq}$ is independent of the direction from which it is attained.