Why is zinc not extracted from zinc oxide through reducing using CO ?

Explanation

`Delta G^(@)` for the conversion of Zn into ZnO is approximately - 650 kJ and for the conversion of CO into `CO_(2)` is approximately - 450 kJ (ie).
`2Zn + O_(2) rarr 2ZnO , Delta G^(@) = -650 kJ`
`2CO + O_(2) rarr 2CO_(2) , Delta G^(@) = -450 kJ`
For the reaction,
`2ZnO + 2CO rarr 2ZN + 2CO_(2), Delta G^(@) = + 200 kJ`
Positive value of shows that the reaction is not feasible. That why, CO cannot be used for the reduction of ZnO into Zn.