Which among the following reactions exhibits $\Delta \mathrm{H}=\Delta \mathrm{U} ?$

Which among the following reactions exhibits $\Delta \mathrm{H}=\Delta \mathrm{U} ?$
  1. $\mathrm{H}_{2(\mathrm{~g})}+\mathrm{Br}_{2(\mathrm{~g})} \rightarrow 2 \mathrm{HBr}_{(\mathrm{g})}$
  2. $2 \mathrm{CO}_{(\mathrm{g})}+\mathrm{O}_{2(\mathrm{~g})} \rightarrow 2 \mathrm{CO}_{2(\mathrm{~g})}$
  3. $\mathrm{PCl}_{5(\mathrm{~g})} \rightarrow \mathrm{PCl}_{3(\mathrm{~g})}+\mathrm{Cl}_{2(\mathrm{~g})}$
  4. $\mathrm{C}_{(\mathrm{s})}+2 \mathrm{H}_2 \mathrm{O}_{(\mathrm{g})} \rightarrow 2 \mathrm{H}_{2(\mathrm{~g})}+\mathrm{CO}_{2(\mathrm{~g})}$

Solution

When $\Delta \mathrm{n}_{\mathrm{g}}=0, \Delta \mathrm{H}=\Delta \mathrm{U}$. For reaction (A), $\Delta \mathrm{n}_{\mathrm{g}}=0$.

Asked in: MHT CET 2023 (09 May Shift 1)

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