For the reaction $NH_4Cl_{(s)} \rightarrow NH_{3(g)} + HCl_{(g)}$,the entropy change is ...... .

Which of the following reactions exhibits a decrease in entropy?

If the enthalpy of fusion of a compound at $27 \, ^\circ C$ is $2930 \, J/mol$,what is the entropy change in $J/mol \cdot K$?

$A$ system of $100 \ kg$ mass undergoes a process in which its specific entropy increases from $0.3 \ kJ \ kg^{-1} \ K^{-1}$ to $0.4 \ kJ \ kg^{-1} \ K^{-1}$. At the same time,the entropy of the surrounding decreases from $80 \ kJ \ K^{-1}$ to $75 \ kJ \ K^{-1}$. Find the $(\Delta S)_{universe}$ in $kJ \ K^{-1}$.

Provide the mathematical equation for entropy change.

Identify the reaction/process in which the entropy decreases.