Write the effect of concentration change on equilibrium and explain it with a suitable example.

(N/A) According to Le Chatelier's principle,when the concentration of any of the reactants or products in a reaction at equilibrium is changed,the composition of the equilibrium mixture changes so as to minimize the effect of the concentration change.
$(i)$ If the concentration of a reactant is increased,the equilibrium shifts in the forward direction to consume the added reactant.
$(ii)$ If the concentration of a product is increased,the equilibrium shifts in the backward direction to consume the added product.
Example: Consider the synthesis of $HI$ at a constant temperature:
$H_{2(g)} + I_{2(g)} \rightleftharpoons 2HI_{(g)}$
If $H_{2(g)}$ is added to the reaction mixture at equilibrium,the system is disturbed. To restore equilibrium,the reaction proceeds in the forward direction,consuming $H_{2}$ and $I_{2}$ to form more $HI$. Consequently,the concentration of $HI$ increases,and the concentration of $I_{2}$ decreases until a new equilibrium state is reached.