Q60 / 200 · NEET 2023 (Manipur) · Chemistry

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).

  • A
    $18 \mathrm{~kJ}$
  • B
    $100 \mathrm{~kJ}$
  • C
    $120.9 \mathrm{~kJ}$
  • Correct answer
    D
    $241.82 \mathrm{~kJ}$

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 $=\frac{483.64}{2} \mathrm{~kJ}$ $=241.82 \mathrm{~kJ}$

Hence, the correct answer is option: 'D'.

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