Question

For the equilibrium

PCl₅ (g) == PCl₃ (g) + Cl₂ (g)

at 298 K, K = 1.8 x 10^-7. What is ΔG° for the reaction?

Answer 1

ΔG° = -2.303 RT log K

= -2.303 x 8.31 JK^-1 mol^-1 x 298 K x log (1.8 x 10^-7)

= -2.303 x 8.31 JK^-1 mol^-1 x 298 K x (0.0334 - 7)

= -2.303 x 8.31 x 298 K x (-6.9664) J mol^-1

= + 39730 J mol^-1

= + 39.73 kJ mol^-1