Question

Identify the correct statement regarding a sponateous process.

• A. for a spontaneous process in an isolated system, the change in entropy is positive
• B. Endothermic processes are never spontaneous
• C. Exothermic processes are always spontaneous
• D. Lowering of energy in the reaction process is the only criterion for spontaneity

Answer 1

The correct option is A for a spontaneous process in an isolated system, the change in entropy is positive

For a spontaneous process, $\Delta G<0$

$\Delta G=\Delta H-T\Delta S<0$

For isolated system, change in enthalpy is 0 hence, $\Delta S$ must be +ve for spontaneous process.

Endothermic process can be spontaneous at higher temperature. $\Delta G$ depends on enthalpy as well as entropy.

For exothermic reactions, $\Delta H<0$ but if $\Delta S<0$, reaction may not be spontaneous depending on the temperature of the system.

The criterion for spontaneity is lowering of energy and increase of entropy.

Hence, option A is correct.