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=30.56 kJ - T xx 0. 0 66 kJ K ^(-1) implies T xx 0 . 0 66 kJ K ^(-1) = 30 . 56 kJ`
`T = ( 30. 56 kJ )/( 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 directionn. Above `463,K, T Delta S gt Delta H , Delta G = Delta H - T Delta S=- ve. ` The reaction will proceed in the reverse direction.
Above `463, K ,T Delta D gt DeltaH, DeltaG= DeltaH - T DeltaS =- ve.` The reaction in spontaneous in the forward direction.