The heat evolved in the conversion of `1 g-` atom of `beta-` sulphur into `alph-` sulphur is `82cal` at `25^(@)C` . If the specific heats of `alpha-` and `beta-` sulphur are `0.163` and `0.171 cal//g`, calculate the heat of transition for `beta-`sulphur into `alpha-` sulphur at `50^(@)C`.

Answer

88.4

Explanation

`beta `- sulphur `toalpha` - sulphur , `DeltaH_1 = 82 " cal at " 25^@C`
Using Kirchoff's equation
`DeltaH_2 - DeltaH_1 = DeltaC_p (T_2 - T_1)`
`DeltaC_p = C_p alpha - S - C_p beta - S`
` = 0.171 - 0.163 = 0.008 cal //g`
`DeltaC_p` is per g and thus `DeltaH_2` and `DeltaH_1` will be per g, i.e.,
`DeltaH_1 = 82/32 cal//g " at" 25^@C`
`DeltaH_2 - DeltaH_1 = DeltaC_p xx [T_2 - T_1]`
`DeltaH_2 -[82/32 + 0.008 xx 25] cal//g`
`=[82/32 + 0.008 xx 25] xx 32 cal //g - atom`
` = 88.4 cal //g - atom`.