Question

Consider the reaction P_(g) + Q_(g) ⇌ PQ_(g) . Diagram ‘X’ represents the reaction at equilibrium.

(White sphere = P, dark sphere = Q)

i. If each molecule (sphere) represents a partial pressure of 1 atm, calculate the value of K_p . 

ii. Predict the change in equilibrium, when the volume is increased by 50 percentage.

Answer 1

i. For the given equilibrium mixture:

Chemical species	P	Q	PQ
Partial pressure	4	6	7

K_p = \(\frac{P_{PQ}}{P_p \times P_Q}\) = \(\frac7{4 \times 6}\) = 0.29

ii. Increasing the volume will shift the equilibrium position to the side with higher number of gaseous moles. In the given reaction, the equilibrium will shift to the left (toward reactant) resulting in an increase in the concentration of P and Q accompanied by a corresponding decrease in concentration of PQ.