The fundamental limitation to the coefficient of performance of a refrigerator is given by

$Assertion :$ In an isolated system,the entropy increases.
$Reason :$ The processes in an isolated system are adiabatic.

One mole of an ideal gas at $300 \ K$ in thermal contact with surroundings expands isothermally from $1.0 \ L$ to $2.0 \ L$ against a constant external pressure of $3.0 \ atm$. In this process,the change in entropy of the surroundings $(\Delta S_{\text{surr}})$ in $J \ K^{-1}$ is $(1 \ L \ atm = 101.3 \ J)$.

Water of mass $m$ gram is slowly heated to increase the temperature from $T_1$ to $T_2$. The change in entropy of the water,given specific heat of water is $1 \ J \ g^{-1} \ K^{-1}$,is

Why can't the efficiency of a heat engine ever be $100 \%$?

An ideal gas in a cylinder is separated by a piston in such a way that the entropy of one part is $S_{1}$ and that of the other part is $S_{2}$. Given that $S_{1} > S_{2}$. If the piston is removed,then the total entropy of the system will be: