Chemistry · Thermodynamics & Thermochemistry

JEE Advanced 2025 — Paper 1 — Question 40

Considering ideal gas behavior, the expansion work done (in kJ ) when 144 g of

water is electrolyzed completely under constant pressure at 300 K is $\qquad$ .

Use: Universal gas constant $(\mathrm{R})=8.3 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ ; Atomic mass (in amu): $\mathrm{H}=1, \mathrm{O}=16$

Answer: 29.88

Numerical answer — enter this value.

$\quad \mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g})$

144 g - - $8 \mathrm{~mol} \quad 8 \mathrm{~mol} \quad 4 \mathrm{~mol}$

$\mathrm{W}=-\mathrm{P} \Delta \mathrm{V}=-(\Delta \mathrm{n}) \mathrm{RT}$

Change in gaseous moles $=12$

$\Rightarrow \quad \mathrm{W}=-\frac{12 \times 8.3 \times 300}{1000} \mathrm{~kJ}=-29.88 \mathrm{~kJ}$ .

Answer key and solution verified before publishing.

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