Among the following processes,for which process is the change in entropy $(\Delta S)$ negative?

The entropy change for the expansion of $2 \, \text{mol}$ of an ideal gas from $2 \, \text{L}$ to $20 \, \text{L}$ at a temperature of $27 \, ^oC$ is ...... $(R = 2 \, \text{cal/mol K})$

$A$ reversible adiabatic process is one in which:

State the characteristics of entropy.

For which one of the following reactions, the entropy change is positive?

Explain entropy and spontaneity.