Question

For a spontaneous process
A) enthalpy change of the system must be negative
B) entropy change of the system must be positive
C) entropy change of the surrounding must be positive
D) entropy change of the system plus surrounding must be positive

Answer 1

Hint:A process is spontaneous when it occurs on its own without external help in the form of a force or energy. A process is nonspontaneous when it does not occurs on its own and you need to provide some external help in the form of a force or energy, for the process to occur.

Complete answer:
Total entropy change is equal to the sum of the entropy change of the system and the entropy change of surrounding. If the total entropy change is equal to zero, the process is an equilibrium process. If the total entropy change is positive, the process is a spontaneous process. If the total entropy change is negative, the process is a non-spontaneous process.

A process will be spontaneous when the randomness of the molecules present in the system increases.
For a spontaneous process entropy change of the system plus surrounding must be positive.

Hence, the correct answer is option (D).

Note: Entropy gives the measure of the disorder or the randomness present in the system. You can use entropy to describe the thermodynamic behaviour of the system. The thermodynamic behaviour of the system can be explained on the basis of properties such as temperature, pressure, heat capacity and entropy.