Calculate $\Delta H$ in $\mathrm{kJ}$ for the following reaction $…

Calculate $\Delta H$ in $\mathrm{kJ}$ for the following reaction $ \mathrm{C}(\mathrm{g})+\mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{CO}_2(\mathrm{~g}) $ Given that, $ \begin{gathered} \mathrm{H}_2 \mathrm{O}(g)+\mathrm{C}(g) \longrightarrow \mathrm{CO}(g)+\mathrm{H}_2(g) ; \\ \Delta H=+131 \mathrm{~kJ} \\ \mathrm{CO}(g)+\frac{1}{2} \mathrm{O}_2(g) \longrightarrow \mathrm{CO}_2(g) ; \\ \Delta H=-282 \mathrm{~kJ} \\ \mathrm{H}_2(g)+\frac{1}{2} \mathrm{O}_2(g) \longrightarrow \mathrm{H}_2 \mathrm{O}(g) ; \\ \Delta H=-242 \mathrm{~kJ} \end{gathered} $
  1. $-393$
  2. $+393$
  3. $+655$
  4. $-655$

Solution

Given, $ \begin{aligned} & \mathrm{H}_2 \mathrm{O}(\mathrm{g})+\mathrm{C}(\mathrm{g}) \longrightarrow \mathrm{CO}(\mathrm{g})+\mathrm{H}_2(g) ; \\ & \Delta H=131 \mathrm{~kJ} \\ & \mathrm{CO}(g)+\frac{1}{2} \mathrm{O}_2(g) \longrightarrow \mathrm{CO}_2(g) ; \\ & \Delta H=-282 \mathrm{~kJ} \\ & \mathrm{H}_2(\mathrm{~g})+\frac{1}{2} \mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{H}_2 \mathrm{O}(\mathrm{g}) \text {; } \\ & \Delta H=-242 \mathrm{~kJ} \\ & \mathrm{C}(\mathrm{g})+\mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{CO}_2(\mathrm{~g}) ; \Delta \mathrm{H}=\text { ? } \\ & \end{aligned} $ On adding Eqs (i), (ii) and (iii), we get Eq (iv) $ \begin{aligned} & \mathrm{H}_2 \mathrm{O}(\mathrm{g})+\mathrm{C}(\mathrm{g}) \longrightarrow \mathrm{CO}(g)+\mathrm{H}_2(g) ; \\ & \Delta H=+131 \mathrm{~kJ} \\ & \mathrm{CO}(\mathrm{g})+\frac{1}{2} \mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{CO}_2(g) \\ & \Delta H=-282 \mathrm{~kJ} \\ & \mathrm{H}_2(g)+\frac{1}{2} \mathrm{O}_2(g) \longrightarrow \mathrm{H}_2 \mathrm{O}(g) \text {; } \\ & \Delta H=-242 \mathrm{~kJ} \\ & \mathrm{C}(\mathrm{g})+\mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{CO}_2(\mathrm{~g}) \\ & \Delta H=(131-282-242) \mathrm{kJ} \\ & =-393 \mathrm{~kJ} \\ & \end{aligned} $

Asked in: AP EAMCET 2008

Practice more Thermodynamics (C) questions on Aicharya