Question

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

Answer 1

Positive change in enthalpy and negative change in entropy.

Step-by-step 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 ΔH<0 and ΔS>0, 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.