Chemistry · Thermodynamics & Thermochemistry

JEE Advanced 2019 — Paper 1 — Question 21

Choose the reaction(s) from the following options, for which the standard enthalpy of reaction is equal to the standard enthalpy of formation.

Option A:
$2 \mathrm{C}(\mathrm{g})+3 \mathrm{H}_{2}(\mathrm{~g}) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(\mathrm{~g})$
Option B:
$\frac{3}{2} \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{O}_{3}(\mathrm{~g})$
Correct
Option C:
$2 \mathrm{H}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(\ell)$
Option D:
$\frac{1}{8} \mathrm{~S}_{8}(\mathrm{~s})+\mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{SO}_{2}(\mathrm{~g})$
Correct

Answer: B, D

Standard enthalpy of formation of a compound is the standard enthalpy when one mole of a compound is formed

from the elements in their stable state of aggregation.

Answer key and solution verified before publishing.

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