Chemistry - Halogen Derivative Question with Solution | TestHub

Key Idea : $\Delta H=\Delta E+\Delta nRT$ $\Delta n=$ number of moles of product - number of moles of reactants $\Delta G=\Delta H-T\Delta S$ For a spontaneous process $\Delta G$ must be negative. ${\mathrm{PCl}}_5(\mathrm{g})\rightleftharpoons {\mathrm{PCl}}_3(\mathrm{g})+{\mathrm{Cl}}_2(\mathrm{g})$ In this reaction $\Delta n=2-1=1$ Thus, $\Delta H$ is positive, $ie,>0$ If $\Delta H$ is positive, then to maintain the value of $\Delta G$ negative, $\Delta S$ should be positive, $ie,\Delta S>0$.