Question

For the reaction,
`4C(graphite) +5H_(2)(g) rarr nC_(4)H_(10)(g)`,
`DeltaH^(Theta) =- 124.73 kJ mol^(-1), DeltaS^(Theta) =- 365.8 J K^(-1) mol^(-1)`
`4C(graphite) +5H_(2)(g) rarr iso-C_(4)H_(10)(g)`
`DeltaH^(Theta) =- 131.6 kJ mol^(-1), DeltaS^(Theta) =- 381.079 J K^(-1) mol^(-1)`
Indicate whther normal butane can be spontaneously converted to iso-butane or not.

Answer 1

For `nC_(4)H_(10)`,
`DeltaG^(Theta) = DeltaH^(Theta) - T DeltaS^(Theta)`
`=- 124.73 - 298 (-365.8 xx 10^(-3))`
`= - 15.72 kJ`
For isobutane (iso-`C_(4)H_(10))`,
`DeltaG^(Theta) =- 131.6 - 298 (-381.079 xx 10^(-3)) =- 18.04 kJ`
For conversion of `nC_(4)H_(10) rarr iso-C_(4)H_(10)`,
`DeltaG^(Theta) =- 18.04 -(-15.72) =- 2.32 kJ`
Negative value shows that the process is spontaneous.