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Question: Answered & Verified by Expert
If $\Delta E$ is the heat of reaction for $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{l})+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(\mathrm{~g})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$
at constant volume, the $\Delta H$ (heat of reaction at constant pressure), at constant temperature is
ChemistryThermodynamics (C)MHT CETMHT CET 2008
Options:
  • A $\Delta H=\Delta E+R T$
  • B $\Delta H=\Delta E-R T$
  • C $\Delta H=\Delta E-2 R T$
  • D $\Delta H=\Delta E+2 R T$
Solution:
1125 Upvotes Verified Answer
The correct answer is: $\Delta H=\Delta E-R T$
We know that, $\Delta H=\Delta E+\Delta n R T$
where, $\Delta n=$ number of moles of gaseous products - number of moles of gaseous reactants
$\begin{array}{lrl} & =2-3= & -1 \\ \text { So, } & & \Delta H=\Delta E-R T\end{array}$

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