Question

Does the number of moles of reaction products increase, decrease or remain same when 

PCl₅(g) ⇌ PCl₃(g) + Cl₂(g)

equilibria is subjected to a decrease in pressure by increasing the volume?

Answer 1

PCl₅(g) ⇌ PCl₃(g) + Cl₂(g)

Here, the forward reaction occurs with increase in number of moles. If the pressure on the system is decreased, the equilibrium will shift in the forward direction which is accompanied by increase in total number of moles. In other words, decrease favours the dissociation of PCl₅ into PCl₃ and Cl₂, increases the dissociation of PCl₅.