The total amount of energy in the universe is fixed,but

For a $Carnot$ engine,the source is at $500 \ K$ and the sink at $300 \ K$. What is the efficiency of this engine?

The enthalpy of vaporization of water is $186.5 \, kJ \, mol^{-1}$. What is the entropy of vaporization in $kJ \, K^{-1} \, mol^{-1}$?

In which of the following processes does the entropy decrease?

In which of the following reactions is $\Delta S$ positive?

If the enthalpy change for the transition of liquid water to steam is $30 \ kJ \ mol^{-1}$ at $27 \ ^oC,$ the entropy change for the process would be ............. $J \ mol^{-1} \ K^{-1}$