For the gas phase reaction, $\mathrm{PCl}_5(\mathrm{~g}) \rightleftharpoons…

For the gas phase reaction, $\mathrm{PCl}_5(\mathrm{~g}) \rightleftharpoons \mathrm{PCl}_3(\mathrm{~g})+\mathrm{Cl}_2(\mathrm{~g})$ Which of the following conditions is correct?
  1. $\Delta \mathrm{H} > 0$ and $\Delta \mathrm{S} < 0$
  2. $\Delta \mathrm{H}=0$ and $\Delta \mathrm{S} < 0$
  3. $\Delta \mathrm{H} > 0$ and $\Delta \mathrm{S} > 0$
  4. $\Delta \mathrm{H} < 0$ and $\Delta \mathrm{S} < 0$

Solution

This is an endothermic reaction, So, $\Delta \mathrm{H} > 0$ Since, number of mole in the product side is more So $\Delta S > 0$.

Asked in: NEET 2008 (Mains)

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