For the reaction $\mathrm{C}_3 \mathrm{H}_8(g)+5 \mathrm{O}_2(g) \rightarrow 3 \mathrm{CO}_2(\mathrm{~g})+4…

For the reaction $\mathrm{C}_3 \mathrm{H}_8(g)+5 \mathrm{O}_2(g) \rightarrow 3 \mathrm{CO}_2(\mathrm{~g})+4 \mathrm{H}_2 \mathrm{O}(l)$ at constant temperature, $\Delta \mathrm{H}-\Delta \mathrm{E}$ is:
  1. +RT
  2. -3 RT
  3. +3 RT
  4. -RT

Solution

$\begin{aligned}
\mathrm{C}_3 \mathrm{H}_{8(g)}+50_{2(g)} & \rightarrow 3 \mathrm{CO}_{2(\mathrm{~g})}+4 \mathrm{H}_2 \mathrm{O}_{(i)} \\
\Delta n & =3-6=-3 \\
\Delta \mathrm{H} & =\Delta \mathrm{E}+\mathrm{P} \Delta \mathrm{V}
\end{aligned}$
or $\Delta \mathrm{H}-\Delta \mathrm{E}=\mathrm{P} \Delta \mathrm{V}$
$\Delta \mathrm{H}-\Delta \mathrm{E}=\Delta \mathrm{nRT}=-3 \mathrm{RT}$

Asked in: NEET 2003

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