Chapter 12

Ethanol boils at \(78.4^{\circ} \mathrm{C}\) and the enthalpy of vaporisation of ethanol is \(42.4 \mathrm{~kJ} \mathrm{~mol}^{-1}\). Calculate the entropy of vaporisation of ethanol.

Calculate the entropy change for the conversion of following: (a) \(1 \mathrm{~g}\) ice to water at \(273 \mathrm{~K}, \Delta H_{\mathrm{f}}\) for ice \(=6.025 \mathrm{~kJ} \mathrm{~mol}^{-1}\). (b) \(36 \mathrm{~g}\) water to vapour at \(373 \mathrm{~K} ; \Delta H_{\mathrm{v}}\) for \(\mathrm{H}_{2} \mathrm{O}=40.63 \mathrm{~kJ} \mathrm{~mol}^{-1}\).

$$ \begin{aligned} &\text { Calculate the value of } \Delta G \text { at } 700 \mathrm{~K} \text { for the reaction } n X \longrightarrow m B .^{-1}\\\ &\text { Given that value of } \Delta H=-113 \mathrm{~kJ} \mathrm{~mol}^{-1} \text { and } \Delta S=-145 \mathrm{JK} \mathrm{mol}^{-1} \text { . } \end{aligned} $$

Calculate the standard free energy change for the reaction, $$ \mathrm{N}_{2(\mathrm{~g})}+3 \mathrm{H}_{2(\mathrm{~g})} \longrightarrow 2 \mathrm{NH}_{3(\mathrm{~g})} \text { at } 298 \mathrm{~K} $$ Given \(\Delta H^{\circ}=-92.4 \mathrm{~kJ}\) and \(\Delta S^{\circ}=-198.3 \mathrm{JK}^{-1} .\) Also, comment on the result.

The equilibrium constant for the reaction given below is \(2.0 \times 10^{-7}\) at \(300 \mathrm{~K}\). Calculate the standard free energy change for the reaction; $$ \mathrm{PCl}_{5(\mathrm{~g})} \rightleftharpoons \mathrm{PCl}_{3(\mathrm{~g})}+\mathrm{Cl}_{2(\mathrm{~g})} $$ Also, calculate the standard entropy change if \(\Delta H^{\circ}=28.40 \mathrm{~kJ} \mathrm{~mol}^{-1}\).