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Calculate Delta(f)H^(@) (in kJ/mol) for ...

Calculate `Delta_(f)H^(@)` (in kJ/mol) for `Cr_(2)O_(3)` from the `Delta_(r)G^(@)` and the `S^(@)` values provided at `27^(@)`
`4Cr(s)+3O_(2)(g)rarr2Cr_(2)O_(3)(s)," "Delta_(r)G^(@)=-2093.4kJ//mol`
`S^(@)("J//K mol") : S^(@)(Cr,s)=24," "S^(@)(O_(2),g)=205," "S^(@)(Cr_(2)O_(3),s)=81`

A

`-2258.1kJ//mol`

B

`-1129.05kJ//mol`

C

`-964.35kJ//mol`

D

None of these

Text Solution

Verified by Experts

The correct Answer is:
B
`Delta_(r)G^(@)=Delta_(r)H^(@)-TxxDelta_(r)S^(@)`
`Delta_(r)S^(@)=2xx81-4xx24-3xx205J//mol`
`therefore" "Delta_(r)H^(@)=-2258.1 kJ//mol`
`Delta_(r)H^(@)=2xxDelta_(f)H^(@)(Cr_(2)O_(3),s)`
`thereforeDelta_(f)H^(@)(Cr_(2)O_(3),s)=-(2258.1)/(2)`
`=-1129.05"kJ/mol"`
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