Question

A reaction is non-spontaneous at any temperature whenDelta H is positive and Delta S is positiveDelta H is positive and Delta S is negativeDelta H is negative and Delta S is negativeDelta H is negative and Delta S is positive

Answer 1

Delta H is positive and Delta S is negative

Step-by-step explanation:

The expression for the standard change in free energy is:

`\Delta G=\Delta H-T* \Delta S`

Where,

`\Delta G` is the change in the Gibbs free energy.

T is the absolute temperature. (T in kelvins)

`\Delta H` is the enthalpy change of the reaction.

`\Delta S` is the change in entropy.

For a reaction to be non spontaneous, it means that:-
`\Delta G>0`

Thus,

`\Delta H-T* \Delta S>0`

For the above conditions to satisfy,
`\Delta H` must be positive and
`\Delta S` must be negative.