Calculate the standard free energy change `(DeltaG^(@))` of the following reaction and say whether it is feasible at 373 K or not `1/2K_(2_((g)))+1/2I_(2_((g)))rarrHI_((g)),DeltaH_(r)^(@) " is " 25.95 kJ mol^(-1)` standard entropies of `HI_((g)) , H_(2_((g))) and I_(2_((g)))` are `206.3 ,140.6 and 118.7 Jk^(-1) mol^(-1)`
Given `S_(I_(2))^(@)=118.7 JK^(-1) mol ^(-1),S_(HI)^(@)=206.3JK^(-1)`
`mol^(-1),S_(H_(2))^(@)=140.6 JK^(-1) mol^(-1)`
Formula : `DeltaS^(@)=S_(HI)^(@)1/2(S_(H_(2))^(@)+S_(I_(2)^(@)))`
`Delta G^(@)=DeltaH^(@) -TDeltaS^(@)`

Explanation

`DeltaH_(f)^(@)=+25.95kjmol^(-1)`
`DeltaS^(@)=sumS_("products")^(@)-sumS_("Reactants")^(@)`
`=206.3-1/2(140+118.7)`
`=206.3-129.65`
`DeltaS^(@)=76.65kJ^(-1)mol^(-1)`
`DeltaG=DeltaG-TDeltaG`
`=25.95-(373xx76xx10^(-3)`
`=25.95-28.59`
`=-2.640kJ^(-1)mol^(-1)`