Question

ΔU^θof combustion of methane is – X kJ mol^–1. The value of ΔH^θ is

(i) = ΔU^θ

(ii) > ΔU^θ

(iii) < ΔU^θ

(iv) = 0

Answer 1

Since ΔH^θ = ΔU^θ + Δn_gRT and ΔU^θ = –X kJ mol^–1,

ΔH^θ = (–X) + Δn_gRT.

⇒ ΔH^θ < ΔU^θ

Therefore, alternative (iii) is correct.