JEE Main 2026 — Chemical Equilibrium Question with Solution
JEE Main 2026 (22 January Shift 1)
Question
Dissociation of a gas takes place according to the following chemical reaction. At equilibrium, the total pressure is 1 bar at 300 K.
The standard Gibbs energy of formation of the involved substances has been provided below:
The degree of dissociation of is given by where . (Nearest integer).
[Given: ]
Assume degree of dissociation is not negligible.
The standard Gibbs energy of formation of the involved substances has been provided below:
The degree of dissociation of is given by where . (Nearest integer).
[Given: ]
Assume degree of dissociation is not negligible.
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Show full solutionCorrect answer: 33
Correct answer
33
Step-by-step explanation
For the dissociation reaction , first calculate the standard Gibbs free energy:
kJ/mol.
Using :
, giving .
For dissociation with degree of dissociation , starting with 1 mole of at 1 bar total pressure:
At equilibrium, moles are for and for , with total moles.
.
Solving: gives or .
Since degree of dissociation is :
gives , so .
kJ/mol.
Using :
, giving .
For dissociation with degree of dissociation , starting with 1 mole of at 1 bar total pressure:
At equilibrium, moles are for and for , with total moles.
.
Solving: gives or .
Since degree of dissociation is :
gives , so .
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This is a previous-year question from JEE Main 2026, covering the Chemical Equilibrium chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.