The value of `triangle_(f)G^(ɵ)(Cr_2O_3)=-540kJmol^-1` and `triangle_(f)G^(ɵ)(Al_2O_3)=-827kJmol^-1`. Is reduction of `Cr_2O_3` possible with Al?

Explanation

(a). `2Cr+(3)/(2)O_2toCr_2O_3`
`triangle_(f)G_a^(ɵ)=-540kJmol^-1`
(b). `2Al+(3)/(2)O_2toAl_2O_3`
`triangle_(f)G_(b)^(ɵ)=-827kJmol^-1`
Required:
c. `Cr_2O_3+2AltoAl_2O_3+2Cr`
`triangle_fG_c^(ɵ)=?`
As `(c)=(b)-(a)`
`triangle_fG_c^(ɵ)=triangle_fG_f^(ɵ)-triangle_fG_a^(ɵ)`
`=(-827+540)kJmol^-1`
`=-287kJmol^-1`
Since `triangle_fG_c^(ɵ)` is negative, hence Al can reduce `Cr_2O_3`.