The gaseous decomposition of phosphorus pentachloride can be written as either
(a) PCl₅(g) → PCl₃(g) + Cl₂(g) or
(b) 2 PCl₅(g) → 2 PCl₃(g) + 2 Cl₂(g).
Calculate Δn_gas for equation (b) and determine whether the entropy change per mole of PCl₅ decomposed is greater than, less than, or equal to that in equation (a).