Question

$PC{l}_5\left(g\right)\rightleftharpoons PC{l}_3\left(g\right)+C{l}_2\left(g\right)$,

For the above given reaction the forward reaction at constant temperature is favoured by:

• A. introducing an inert gas at constant volume
• B. introducing chlorine gas at constant volume
• C. introducing an inert gas at constant pressure
• D. introducing $PC{l}_5$ at constant volume

Answer 1

Answer: (C), (D)

The correct options are
C introducing an inert gas at constant pressure
D introducing $PC{l}_5$ at constant volume

A. When an inert gas is added to the system in equilibrium at constant volume, the total pressure will increase. But the concentrations of the products and reactants will not change.

Hence, when an inert gas is added to the system in equilibrium at constant volume there will be no effect on the equilibrium.

B. Introducing chlorine will increase the reaction constant and to attain an equilibrium, the reaction will move to reduce moles of chlorine gas. Hence B is incorrect.

C. Introducing inert gas at constant pressure increases the total volume and this, in turn, reduces the concentration of individual reactant and product. However, the power is 2-1=1, hence the reaction constant decreases.

So, reaction moves forward.
D. Introducing $PC{l}_5$ decreases the reaction constant as its concentration comes in the denominator. Hence, the reaction will move in the forward direction to increase reaction constant and attain equilibrium.

Hence, the correct options are $\text{D}$