1.

The minimum voltage required to electrolyse alumina in the Hall-Heroul process is [Given, `DeltaG^(@)_(f)(A1_(2)O_(3)) =- 1520kJ//mol` and `DeltaG^(@)_(f)(CO_(2)) = 394kJ//mol]`A. `0.8 V`B. `1,60 V`C. `2.8 V`D. `3.0 V`

Answer» `(b) 2AI_(2)O_(3)+3C to 4AI + 3CO_(2)`
`Delta_(f)G^(@)=3DeltaG^(@)(CO_(2))`
`=3xx(-394)-2xx(-1520)=1859kJ`
`=1858xx10^(3)J`
`:. nFE^(@) = 1858 xx 10^(3)" "(n=12 "electrons")`
`:. E^(@)=(1858xx10^(3))/(12xx96500)=1.60 V`


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