For the reaction `Ag _(2)O (s) hArr 2 Ag (s) + 1//2 O _(2) (g),` calculate the temperature at which free energy change `DeltaG` is equal to zero. `DeltaH` for the reaction `=+30.56 kJ` and `DeltaS=+0.066kJK^(-1)` at 1 atm pressure. Predict the nature of the reaction (i) below this temperature, (ii) above this temperature.

Explanation

According to Gibbs-Helmhoitz equation,` Delta G =Delta H- T Delta S`
`0=20.56 kJ - T xx 0.066 kJ K ^(-1) implies T xx 0.066 kJ K ^(-1)=30.56 kJ`
`T = ( 30.56kJ)/(0.066 kJ K ^(-1)) = 463.03 K~~463 K`
Below `463 K, T Delta S lt Delta H , Delta G = Delta H - T Delta S = + ve.` the reaction will proceed in the reverse direction.
Above `463K, T Delta S gt Delta H, Delta G = Delta H - T Delta S=- ve. ` The reaction is spontaneous in the forward direction .