In pyro metallurgy the metals are extracted from ores and concentrates by heat treatment. This involves conversion to metal oxide. This is followed by the reduction of the oxide to the metal using carbon or carbon monoxide.
`4Cr(s)+3O_(2)(g) to 4Cr_(2)O_(3)(s),`
`" " DeltaG^(@)=1500kJ//"mol at" 1200^(@)C`
`2Mn(s)+O_(2)(g) to 2MnO(s),`
`" " DeltaG^(@)=-600kJ//"mol at" 1200^(@)C`
`2C(s)+O_(2)(g) to 2CO(g),`
`" " DeltaG^(@)=-550kJ//"mol at" 1200^(@)C`

Options

A. C(s) can reduce MnO(s) under given condition
B. C(s) can reduce Cr_(2)O_(3)(s) under given condition0
C. Neither MnO(s) nor `Cr_(2)O_(3)(s)` be reduced by C(s) under given condition
D. Both will be reduced simultaneously if carbon is passed over a mixture `MnO(s) and Cr_(2)O_(3)(s)`.

Answer

B

Explanation

For a reaction to occur `DeltaG^(@) lt 0`
`2MnO+2C to 2Mn+CO,`
`" " DeltaG=50kJ//mol("not feasible")`
`(2)/(3)Cr_(2)O_(3)+2C to (4)/(3)Cr+2CO,`
`" " DeltaG=-50kJ//mol("Feasible")`.