What is meant by absolute entropy?

For the vaporization of water at $1 \, \text{atm}$ pressure,the liquid water and water vapor are in equilibrium. What is the temperature in $K$?
$H_2O_{(l)} \rightleftharpoons H_2O_{(g)}$ [at $1 \, \text{atm}$ pressure] [$\Delta S = 120 \, J K^{-1}$ and $\Delta H = +45.0 \, kJ$]

An irreversible process occurring isothermally in an isolated system leads to

For which of the following reactions will $\Delta S$ be maximum?

What is entropy?

Calculate $\Delta S_{total}$ for a certain reaction at $298 \ K$ if $\Delta H^{\circ} = -208.6 \ kJ$ and $\Delta S^{\circ} = -36 \ J \ K^{-1}$. (in $J \ K^{-1}$)