For a given reaction, `Delta H = 35.5 kJ mol^(-1)` and `Delta S = 83.6 JK^(-1) mol(-1)`. The reaction is spontaneous at : (Assume that `Delta H and Delta S` do not vary with temperature)

Options

A. `T lt425 K`
B. `T gt 425 K`
C. All temperatures
D. `T gt 298 K`

Answer

B

Explanation

`DeltaS= DeltaH - T DeltaS`
For the reaction to be spontaneous , `DeltaG = - ve`
As`DeltaH` and`DeltaS` both are positive,`DeltaG` can be `-ve` only if`T DeltaS gt DeltaH` or`T gt ( DeltaH)/( DeltaS)`
`i.e,T gt ( 35.5xx 1000J)/( 83.6JK^(-1)) ` or `T gt 425 K`