Consider the following reaction: $2 \mathrm{H}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \rightarrow 2…
Consider the following reaction:
$2 \mathrm{H}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{H}_2 \mathrm{O}(\mathrm{g}) \Delta_{\mathrm{r}} \mathrm{H}^{\circ}=-483.64 \mathrm{~kJ}$. What is the enthalpy change for decomposition of one mole of water? (Choose the right option).
$18 \mathrm{~kJ}$
$100 \mathrm{~kJ}$
$120.9 \mathrm{~kJ}$
$241.82 \mathrm{~kJ}$
Solution
$2 \mathrm{H}_2 \mathrm{O}(\mathrm{g}) \longrightarrow 2 \mathrm{H}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g})$
$\Delta \mathrm{H}^{\circ}=483.64 \mathrm{~kJ}$
For decomposition of 2 moles of $\mathrm{H}_2 \mathrm{O}$, enthalpy change $=483.64 \mathrm{~kJ}$
For decomposition of 1 mole of $\mathrm{H}_2 \mathrm{O}$, enthalpy change $=\frac{483.64}{2} \mathrm{~kJ}$
$=241.82 \mathrm{~kJ}$