Question

Which of the following factors will not disturb the equilibrium state of the reaction? $H_2\left(g\right)+I_2\left(g\right)\rightleftharpoons 2HI\left(g\right){\Delta }_{r}H=+3000\text{cal}$

• A. Change in temperature
• B. Addition of catalyst
• C. Addition of $H_2$
• D. All of the above.

Answer 1

The correct option is B Addition of catalyst

As per Le- Chatelier's principle,
Since this reaction is an endothermic reaction, change in temperature will affect the equilibrium state. An increase in temperature will favor the products while a decrease in temperature will favor the reactant side.

Addition of catalyst does not disturb the equilibrium and the equilibrium constant. It increases the rate of forward and backward rection to the same extent but equilibirum remains unaltered.

Effect of change in concentration of reactant and/or product:
In an equilibrium increasing the concentrations of reactants results in shifting the equilibrium in favour of products. So, addition of $H_2$ will shift the equilibrium toward the right.


Theory:

Addition of Catalyst :
Catalyst is a substance which can change the speed of a chemical reaction without itself getting consumed. The function of the catalyst is to simply reach the point of equilibrium in less/more time than usual.
So a catalyst can only have its effect on the rate of the reaction and not on the equilibrium constant of the reaction.