Question

The reaction system: POCl3(g) POCl(g) + Cl2(g) is at equilibrium. Which of the following statements describes the behavior of the system if POCl is added to the container?(A) The forward reaction will proceed to establish equilibrium.(B) The reverse reaction will proceed to establish equilibrium.(C) The partial pressures of POCl3 and POCl will remain steady while the partial pressure of chlorine increases.(D) The partial pressure of chlorine remains steady while the partial pressures of POCl3 and POCl increase.(E) The partial pressure of chlorine will increase while the partial pressure of POCl decreases.

Answer 1

Answer: (B) The reverse reaction will proceed to establish equilibrium.

Explanation:

Any change in the equilibrium is studied on the basis of Le-Chatelier's principle.

This principle states that if there is any change in the variables of the reaction, the equilibrium will shift in the direction to minimize the effect.

For the given equation:

$POCl_3(g)\leftrightharpoons POCl(g)+Cl_2(g)$

Given : when $POCl$ is added to the system

If the concentration of $POCl$ that is the product is increased, so according to the Le-Chatlier's principle, the equilibrium will shift in the direction where decrease of concentration of $POCl$ takes place. Therefore, the equilibrium will shift in the left or backward direction.

Thus the reaction will shift towards reactants to reestablish equilibrium and thus partial pressure of $POCl$ and $Cl_2(g)$  decreases and the partial pressure of $POCl_3$ increases.