Calculate the standard Gibbs free energy of reaction in each of the following using the standard molar entropy values given. Express your answers to 3 significant figures in kJmol¹, and in each case state whether the reaction is spontaneous or not under standard conditions.

(Values for S^θin J K^–1 mol^–1: Ag₂CO₃(s) = 167.4,

Ag₂O(s) = 121.3, CH₄(g) = 186.2, Cl₂(g) = 165,

CO₂(g) = 213.6, H₂(g) = 130.6, HCl(g) = 186.8,

H₂O(l) = 69.9, Mg(s) = 37.2, MgCl₂(s) = 89.6,

Na(s) = 51.2, Na₂O₂(s) = 95.0, O₂(g) = 205.0)

a. H₂(g) + Cl₂(g) → 2HCl(g)                                           ΔH^θreaction=–184.6 kJ mol^–1

b. CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)                      ΔH^θreaction=–890.3 kJ mol^–1

c. 2Na(s) + O₂(g) → Na₂O₂(s)                                      ΔH^θreaction=–510.9 kJ mol^–1

d. Mg(s) + Cl₂(g) → MgCl₂(s)                                       ΔH^θreaction=–641.3 kJ mol^–1

e. Ag₂CO₃(s) → Ag₂O(s) + CO₂(g)                               ΔH^θreaction=+167.5 kJ mol^–1