Question

For the reaction Ag₂O_(s) → 2Ag_(s) + 1/2O_2(g) : ∆H = 30.56 kJ mol^-1 and ∆S = 6.66 JK^-1 mol^-1 (at 1 atm). Calculate the temperature at which AG is equal to zero. Also predict the direction of the reaction (i) at this temperature and (ii) below this temperature.

Answer 1

∆H = 30.56 kJ mol^-1 

∆H = 30560 J mol^-1 

∆S = 6.66 x 10^-3 kJ K^-1 mol^-1 

T = ? at which ∆G = 0 

∆G = ∆H – T∆S 

0 = ∆H – T∆S

T = ΔH / ΔS

t = 4589 K

(i) At 4589K ; ∆G = 0, the reaction is in equilibrium. 

(ii) At temperature below 4598 K, ∆H > T ∆ S ∆G = ∆H – T∆S > 0, the reaction in the forward direction, is non-spontaneous. In other words the reaction occurs in the backward direction.