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

In which of the following processes does entropy decrease?

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 ............. $J \ mol^{-1} \ K^{-1}$

Which of the following statements is incorrect when a system consisting of an ideal gas undergoes a change of state?

At $25\,^oC$ and $1\,atm$ pressure,mercury reacts with chlorine to form mercurous chloride: $2Hg + Cl_2 \to Hg_2Cl_2; \Delta H = -31.3\,kcal$. What is the entropy change of the reaction at $25\,^oC$?

For a reversible expansion of $5 \, \text{mol}$ of an ideal gas at $27 \, ^\circ\text{C}$ from a volume of $8 \, \text{dm}^3$ to $80 \, \text{dm}^3$,the change in entropy is ...... $J \, K^{-1}$.