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`

Options

A. `-2258.1 kJ//mol`
B. `-1129.05 kJ//mol`
C. `-964.35 kJ//mol`
D. `3462kJ//mol`

Answer

B

Explanation

`Delta_(r)G^(@) = Delta_(r)H^(@)-T xx Delta_(r)S^(@)`
`Delta_(r)S^(@) = 2 xx 81 -4xx 24 -3 xx 205 J//mol`
`:. Delta_(r)H^(@) = -2258.1 kJ//mol`
`Delta_(r)H^(@) = 2 xx Delta_(f)H^(@)(Cr_(2)O_(3), s)`
`:. Delta_(f)H^(@)(Cr_(2)O_(3), s) = -(2258.1)/(2)`
`= -1129.05 kJ//mol`.