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. `-357kJ`
B. `-731kJ`
C. `-773kJ`
D. `-229kJ`

Answer

B

Explanation

For the reaction
`2ZnSto2Zn+S_(2),DeltaG_(1)^(@)=293kJ`……….(i)
`2Zn+O_(2)to2ZnO,DeltaG_(2)^(@)=-480kJ`……………….(ii)
`S_(2)+2O_(2)to2SO_(2),DeltaG_(3)^(@)=-544kJ`……………(iii)
`DeltaG^(@)` for the reaction
`2ZnS+3O_(2)to2ZnO+2SO_(2)`
can be obtained by adding eqn. (1),(2) and (3)
`implies DeltaG^(@)=293-480-544=-731kJ`