The factor of `DeltaG` values is important in metallurgy. The `DeltaG` values for the following reactions at 800°C are given as :
`S_(2)(s) + 2O_(2)(g) to 2SO_(2)(g), DeltaG =-544 kJ`
`2Zn(s) + S_(2)(s) to 2ZnS(s), DeltaG=-293` kJ
`2Zn(s) + O_(2)(g) to 2ZnO(s), DeltaG = -480` kJ
Calculate the `DeltaG` for the reaction:
`2ZnS(s) + 3O_(2)(g) to 2ZnO(s) + 2SO_(2)(g)`

Options

A. `-731kJ`
B. `- 787 kJ`
C. `- 534kJ`
D. `- 554kJ`

Answer

a

Explanation

From the given reactions,
`Delta_(f)G^(@) (SO_(2)) = - ( 544)?( 2) = - 272 kJ mol^(-1)`
`Delta_(f)G^(@) ( ZnS) = - ( 293)/( 2) = - 146 .5kJmol^(-1)`
`Delta_(f)G^(@) (ZnO)= - ( 480)/( 2) = - 240 kJ mol^(-1)`
For the required reaction
`Delta_("reaction") G^(@) = SigmaDelta_(f)G^(@) (`Products) - `Delta_(f)G^(@) (` Reactants)
` [2 Delta_(f)G^(@) (ZnO) + 2Delta_(f)G^(@) ( SO_(2))]- [2Delta_(f)G^(@) ( ZnS) + 3 xx 0]`
`= - 480 + ( - 544) - ( - 293) = - 731kJ`