Consider the reaction : 2 H 2 S ( g )+3 O 2 ( g ) rightarrow 2 H 2 O ( l )+2 SO 2 ( g ) The magnitude of enthalpy change for the reaction in kJ mol -1 is \ \ \ \ . (Nearest integer) Given : Δ f H ominus ( H 2 S )=-20.1 kJ mol -1 begin aligned & Δ f H Theta ( H 2 O )=-286.0 kJ mol -1 & Δ f H Theta ( SO 2 )=-297.0 kJ mol -1 end aligned

Chemistry · Thermodynamics & Thermochemistry

JEE Main 2026 — 8 April, Evening Shift — Question 62

Consider the reaction : $2 \mathrm{H}_{2} \mathrm{~S}(\mathrm{~g})+3 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+2 \mathrm{SO}_{2}(\mathrm{~g})$ The magnitude of enthalpy change for the reaction in $\mathrm{kJ} \mathrm{mol}^{-1}$ is $\_\_\_\_$ . (Nearest integer)

Given : $\Delta_{f} \mathrm{H}^{\ominus}\left(\mathrm{H}_{2} \mathrm{~S}\right)=-20.1 \mathrm{~kJ} \mathrm{~mol}^{-1}$

\begin{aligned} & \Delta_{f} \mathrm{H}^{\Theta}\left(\mathrm{H}_{2} \mathrm{O}\right)=-286.0 \mathrm{~kJ} \mathrm{~mol}^{-1} & \Delta_{f} \mathrm{H}^{\Theta}\left(\mathrm{SO}_{2}\right)=-297.0 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned}

Answer: 1126

Numerical answer — enter this value.

Step-by-step solution

$\quad \Delta_{\mathrm{r}} \mathrm{H}^{\circ}=\Sigma \Delta \mathrm{H}_{\mathrm{f}}{ }^{\circ}$ (product) $-\Sigma \Delta \mathrm{H}_{\mathrm{f}}{ }^{\circ}$ (Reactant) $\Delta_{\mathrm{r}} \mathrm{H}^{\circ}=2 \times \Delta \mathrm{H}_{\mathrm{f}}^{\circ}\left(\mathrm{SO}_{2}, \mathrm{~g}\right)+2 \times \Delta \mathrm{H}_{\mathrm{f}}^{\circ}\left(\mathrm{H}_{2} \mathrm{O}, \ell\right)$

-2 \times \Delta \mathrm{H}_{\mathrm{f}}^{\circ}\left(\mathrm{H}_{2} \mathrm{~S}, \mathrm{~g}\right)

$\Delta_{\mathrm{r}} \mathrm{H}^{\circ}=2 \times(-297)+2 \times(-286)-2(-20.1)$ $=-594-572+40.2$ $\Delta_{\mathrm{r}} \mathrm{H}^{\circ}=-1125.8 \mathrm{~kJ} / \mathrm{mol}$ . $\left|\Delta_{\mathrm{r}} \mathrm{H}^{\circ}\right|=1125.8 \mathrm{~kJ} / \mathrm{mol}$ .

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 8 April, Evening Shift
Subject: Chemistry
Chapter: Thermodynamics & Thermochemistry
Topic: Thermochemistry and Enthalpy Changes