Which of the following combinations will result in a reaction that is never spontaneous?

positive enthalpy change and positive entropy change

positive enthalpy change and negative entropy change

negative enthalpy change and positive entropy change

Positive change in enthalpy and negative change in entropy.

Explanation:

Remember that any spontaneous process must lead to a net increase in entropy.

When ΔH>0 and ΔS>0, the reaction proceeds spontaneously at high temperatures and proceeds spontaneously in the reverse direction at low temperatures.

When ΔH>0 and ΔS<0, the reaction proceeds spontaneously in the reverse direction.

When ΔH0, the reaction proceeds spontaneously at all temperatures.

When ΔH<0 and ΔS<0, the reaction proceeds spontaneously at low temperatures and proceeds spontaneously in the reverse direction at high temperatures.