Calculate $\Delta_r \mathrm{H}\left(\mathrm{kJ} \mathrm{mol}^{-1}\right)$ of the following reaction…

Calculate $\Delta_r \mathrm{H}\left(\mathrm{kJ} \mathrm{mol}^{-1}\right)$ of the following reaction $\begin{array}{cc}\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}(\mathrm{I})+7 / 2 \mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{CO}_2(\mathrm{~g})+3 \mathrm{H}_2 \mathrm{O}(\mathrm{I}) \\ \text { Molecule } & \Delta_{\mathrm{f}} \mathrm{H}^0\left(\mathrm{~kJ} \mathrm{~mol}^{-1}\right) \\ \mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}(\mathrm{I}) & -280 \\ \mathrm{CO}_2(\mathrm{~g}) & -400 \\ \mathrm{H}_2 \mathrm{O}(\mathrm{l}) & -290\end{array}$
  1. $-1950$
  2. $-1100$
  3. $-1390$
  4. $-700$

Solution

$\Delta_{\mathrm{r}} \mathrm{H}^{\circ}=2 \Delta_{\mathrm{f}} \mathrm{H}_{\mathrm{CO}_2}^{\circ}+3 \Delta_{\mathrm{f}} \mathrm{H}_{\mathrm{H}_2 \mathrm{O}}^{\circ}-\Delta_{\mathrm{f}} \mathrm{H}_{\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}}^{\circ}$ $\begin{aligned} & =2(-400)+3(-290)-(-280) \mathrm{kJ} \\ & =-800-870+280=-1390 \mathrm{~kJ}\end{aligned}$

Asked in: AP EAMCET 2022 (08 Jul Shift 1)

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