Question

A chemical reaction has an increase in entropy and a decrease in enthalpy. What is known about the spontaneity of the reaction?

Answer 1

Answer: Reaction is spontaneous at all temperatures.

Explanation:

According to Gibb's equation:

$\Delta G=\Delta H-T\Delta S$

$\Delta G$ = Gibbs free energy

$\Delta H$ = enthalpy change

$\Delta S$ = entropy change

T = temperature in Kelvin

$\Delta G$= +ve, reaction is non spontaneous

$\Delta G$= -ve, reaction is spontaneous

$\Delta G$= 0, reaction is in equilibrium

Thus when $\Delta H$ = -ve (decrease in enthalpy)

$\Delta S$ = +ve (increase in entropy)

$\Delta G=(-ve)-T(+ve)$

$\Delta G=(-ve)(-ve)=-ve$  

Thus Reaction is spontaneous at all temperatures.

Answer 2

A chemical reaction has an increase in entropy and a decrease in enthalpy. The chemical reaction is spontaneous. A chemical reaction is spontaneous if it has an entropy greater than zero and an enthalpy less than 0