For the reaction

PCl₅(g) ⇌ PCl₃(g) + Cl₂(g)

The reaction given is an example of decomposition reaction and we know that decomposition reactions are endothermic in nature, i.e., ΔH > 0.
Further Δn = (1+1) – 1 = +1
Hence more number of gaseous molecules are present in products which shows more randomness i.e., ΔS > 0 (ΔS is positive)