Which of the following processes is associated with an increase in entropy?
$(I)$ Melting of a solid
$(II)$ Mixing of gases
$(III)$ Compression of a gas
$(IV)$ Expansion of a gas

What is the entropy of vaporisation of water at $100\,^{\circ}C$,if the molar heat of vaporisation is $9710\,cal/mol$?

Identify from the following physical transformations that exhibits a decrease in entropy.

$30.4 \, kJ$ of heat is required to melt one mole of sodium chloride and the entropy change at the melting point is $28.4 \, J \, K^{-1} \, mol^{-1}$ at $1 \, atm$. The melting point of sodium chloride is $........... \, K$ (Nearest Integer).

$A$ 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 $kJ \ K^{-1}$.

In which of the following processes is $\Delta S$ negative?