At 298 K, the gas-phase decomposition of substance X has an equilibrium constant of K=2.5×10−8. Calculate the standard Gibbs free-energy change ΔG∘ for the reaction in kJ mol⁻¹.
(R = 8.314 J mol⁻¹ K⁻¹)
a) −43kJ mol−1
b) +3.6kJ mol−1
c) +43kJ mol−1
d) +19kJ mol−1