Question

For the reaction $PC{l}_5\left(g\right)\rightleftharpoons PC{l}_3\left(g\right)+C{l}_2\left(g\right)$; the forward reaction at constant temperature is favoured by

• A. Adding an inert gas at a constant volume
• B. Adding an inert gas at a constant pressure
• C. Adding $C{l}_2$at a constant volume
• D. Increasing the volume of the container

Answer 1

Answer: (B), (D)

The correct options are
B Adding an inert gas at a constant pressure
D Increasing the volume of the container

Option A
Adding inert gas at constant volume has no effect on equilibrium as the partial pressure remains the same.

Option B
Adding inert gas at a constant pressure increases the overall volume, reduces the concentration of all reactants, changing the partial pressure. The system tries to undo that change and to increase the concentration goes in the direction where moles increase, which is the forward direction in this case.
Option C
addition of $C{l}_2$ at constant volume causes the reaction to move backwards
Option D
This has a similar effect as adding an inert gas at constant volume. The concentration decreases, decreasing the partial pressure, the reaction moves forward to increase the number of moles.