Question

Assertion: Addition of inert gases at equilibrium at constant pressure will support the dissociation of $PC{{l}_{5}}$ at constant temperature.
Reason: The addition of inert gas at constant volume will not affect the equilibrium.
A.Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B.Both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion
CAssertion is correct, but Reason is incorrect
D.Assertion is incorrect, but Reason is correct

Answer 1

In chemical equilibrium, no net change in the amounts of reactants and products occurs. In this, the opposing reaction moves with the equal rate and no net change in the amount of the substances is observed. Dissociation is defined as the breaking of a reactant into simpler products.

Complete step by step answer:
Let us see the reaction first,
$PC{{l}_{5}}\rightleftharpoons PC{{l}_{3}}+C{{l}_{2}}$
Le Chatelier’s principle stated that the change in the temperature, volume, pressure or concentration will give us a change in the system to achieve a new equilibrium state. This principle tells us about the equilibrium of the reaction.
Change in concentration:
In a chemical reaction, we can see when the concentration of the product is reduced, then it will shift the equilibrium of the reaction to the right or if the reactant is removed, then the equilibrium will shift to the left.
Change in temperature:
In an endothermic reaction, when we increase the temperature, this means that we are adding more reactant to the system and hence by the Le Chatelier’s’ principle, the equilibrium will shift to the right. Similarly, if we decrease the temperature in an endothermic reaction, the equilibrium will shift to the left. In an exothermic reaction, when temperature is increased the equilibrium will shift to the left and if, the temperature is decreased, the temperature will shift to the right.
Change in pressure:
Change in the pressure or volume will result in the change in number of moles. If we increase the temperature and decrease the volume, the equilibrium will shift to the side of the reaction that contains less number of moles. When pressure is decreased and volume is increased, the equilibrium will shift to the side of the reaction that contains less number of moles, that is, it will shift to the right because reactants contain less number of moles.
Addition of inert gas:
Addition of inert gas will have no effect on equilibrium because inert gas will not react with the either of the products or reactants.
In dissociation reaction, the number of moles in the product are more than the reactant, therefore, when an inert gas is added at constant temperature and pressure, the volume will increase and so, the number of moles will also be increased. As we know that the number of moles is more in product, therefore, dissociation will take place. The assertion is correct.
Addition of inert gas at constant volume will increase the pressure but shows no change in the concentration of product and reactant. Therefore the reason is correct but it is not a correct explanation of assertion.
Therefore, the correct option is (B) Both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion.

Note: The endothermic process is defined as a process in which the enthalpy of the system will increase and an exothermic process is defined as a process in which the enthalpy of the system will decrease.
-The decrease in enthalpy will result in a spontaneous reaction and increase in enthalpy will result in non – spontaneous reaction.
-In conclusion we have discussed that in addition to inert gas at constant pressure, will increase the number of moles and therefore the dissociation of phosphorus pentachloride will shift to the right. At constant volume, when inert gases are added it shows no change in concentration of reactants and products