JEE Main · Chemistry · Equilibrium

Chemical Equilibrium: JEE Main previous year questions

Name: Chemical Equilibrium: JEE Main previous year questions
Creator: Lumi

48 questions in the 108 JEE Main shifts Lumi analysed, in 7 of 8 years. Pattern: Asked most years. 20 came in 2024–26. Here is how it is asked and which ideas come back.

Questions: 48; in 45 of 108 shifts
Years asked: 7/8; last asked 2026
Chance in a shift: 47%; calibrated model, how we compute it
Weighted estimate: 0.5; model; history: 0.4 a shift on average, typically 0.3–0.6

Key findings

01
Asked in 7 of 8 years with analysed shifts and in 45 of 108 shifts: 48 questions, #62 of 196 topics.
02
46% of its questions since 2020 tested an idea no earlier year had asked; 9 repeated an idea from the year before.
03
The most repeated idea is Equilibrium Constant for Modified Equations, asked 9 times in 9 shifts (2020, 2022, 2024, 2026), most often as “equilibrium constant of combined reactions”.
04
JEE Main has asked 17 of the 45 ideas in this topic; 24 have never been asked, directly or inside another question.
05
Mostly asked as numerical value (50%); 50% need a numerical answer, 35% are easy and 2% hard. It went up from 0.3 to 0.6 questions a shift since 2024.
06
The skill tested most is calculation (56%), then multi-step (15%).

Questions a shift, year by year

Out of the 25 Chemistry questions in a shift. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift.

Raw count: 2017: 0 in 1 shift · 2020: 5 in 12 shifts · 2021: 9 in 24 shifts · 2022: 9 in 24 shifts · 2023: 5 in 12 shifts · 2024: 8 in 18 shifts · 2025: 5 in 8 shifts · 2026: 7 in 9 shifts.

Up to 2023: 0.3; a shift, of 25
Since 2024: 0.6; +0.3
Usual gap: 1.0 yrs; between years asking it
Shifts with it: 45/108; 42% of analysed shifts

Recent framings

equilibrium constant from combined reactions
numerical: partial pressure from coupled equilibria
numerical: partial pressure from Kc and inert gas

Revise first

Equilibrium Constant for Modified Equations · asked 2020, 2022, 2024, 2026
Kp for PCl5 Dissociation Type Reactions · asked 2021, 2024, 2025, 2026
Dalton's Law in Kp Calculations · asked 2023, 2025, 2026

How it is asked

Difficulty, format and skill

Across all 48 questions on Chemical Equilibrium since 2017.

Difficulty

QUESTIONS

1730

Easy17 · 35%
Medium30 · 63%
Hard1 · 2%

Format

Numerical value · 24 Q50%
Single correct · 21 Q44%
Two statements · 1 Q2%
Other · 1 Q2%
Diagram based · 1 Q2%

Skill tested

Calculation · 27 Q56%
Multi-step · 7 Q15%
Application · 6 Q13%
Conceptual · 4 Q8%
Data or graph · 3 Q6%
Recall · 1 Q2%

Repeats

New idea, or one asked before?

Each column is a year. Blue questions tested an idea no earlier year had asked; navy ones went back to an idea from an earlier year. 2017 is the first year, so everything in it counts as new. Heights are question counts, and Lumi analysed 1 to 24 shifts a year, so compare the split inside a column rather than heights across years.

’17’20’21’22’23’24’25’26

Idea asked for the first time
Idea asked in an earlier year

Coverage of the topic

JEE Main has asked 17 of the 45 ideas in this topic. 24 have never been asked yet.

1724

Asked directly17 · 38%
Touched inside another question4 · 9%
Never asked24 · 53%

Ideas come from Lumi’s JEE syllabus map. A never-asked idea is not a safe skip: across all of JEE Main, 22% of questions since 2024 tested an idea no earlier year had asked.

Drill down

Chapter, idea, question

Every idea JEE Main tested in this topic, with its eight years. Open one to read the questions.

chapterAskedShareYears’17’20’21’22’23’24’25’26

Open46 · 96%96%7/85895856
15 ideas inside
- OpenRepeated9 · 20%20%4/82322
- OpenRepeated5 · 11%11%4/82
- OpenRepeated4 · 9%9%3/82
- OpenRepeated4 · 9%9%2/822
- OpenRepeated4 · 9%9%2/83
- OpenRepeated4 · 9%9%4/8
- OpenRepeated3 · 7%7%3/8
- OpenRepeated3 · 7%7%3/8
- OpenRepeated2 · 4%4%2/8
- OpenRepeated2 · 4%4%2/8
- OpenRepeated2 · 4%4%2/8
- Open1 · 2%2%1/8
- Open1 · 2%2%1/8
- Open1 · 2%2%1/8
- Open1 · 2%2%1/8
Open1 · 2%2%1/8
Open1 · 2%2%1/8

Squares are the 8 years with analysed shifts, 2017 to 2026. A number is the questions that year when there is more than one; the shade is scaled to one shift, so a year with more analysed shifts (1 to 24 a year) does not look darker. Share is of the level above.

Ideas

Every idea inside this topic

17 different ideas were tested; 11 came more than once.

Equilibrium Constant for Modified Equations9×
equilibrium constant of combined reactions
Single correct · 9 shifts · 1 numerical
Degree of Dissociation5×
degree of dissociation from kp
Numerical value · 5 shifts · 3 numerical
Kp for PCl5 Dissociation Type Reactions4×
kp expression from extent of dissociation
Single correct · 4 shifts · 1 numerical
Kc and Kp Relationship4×
kc from kp
Numerical value · 4 shifts · 3 numerical
Kp Expression via Partial Pressures4×
kp from equal molecules of reactants and product
Numerical value · 4 shifts · 2 numerical
ICE Table Construction4×
equilibrium concentration from kc
Numerical value · 4 shifts · 4 numerical
Dalton's Law in Kp Calculations3×
partial pressure from kc and inert gas
Numerical value · 3 shifts · 2 numerical
Standard Gibbs Free Energy and Equilibrium Constant3×
standard gibbs energy from dissociation
Numerical value · 3 shifts · 3 numerical
Heterogeneous Equilibrium2×
partial pressure from coupled equilibria
Numerical value · 2 shifts · 2 numerical
Kc Expression2×
write kc expression for reaction
Single correct · 2 shifts
Le Chatelier's Principle2×
new equilibrium concentration after adding reactant
Numerical value · 2 shifts · 1 numerical
Temperature Dependence of K (Van 't Hoff Equation)1×
enthalpy from equilibrium constant data
Numerical value · 1 shift · 1 numerical
Effect of Catalyst on Equilibrium1×
statement i/ii on catalyst and equilibrium
Two statements · 1 shift
Inert Gas Effect at Constant Pressure1×
effect of inert gas on equilibrium
Single correct · 1 shift
Adding Pure Solid or Liquid1×
le chatelier effect of adding pure solid
Single correct · 1 shift
Equilibrium Constant from Rate Constants1×
equilibrium constant from forward and backward rate terms of rate law
Numerical value · 1 shift · 1 numerical
Rate-Time Graph Analysis1×
graph interpretation of rate vs time at equilibrium
Diagram based · 1 shift

Idea	Times	Shifts	Format	Numerical
Equilibrium Constant for Modified Equationsequilibrium constant of combined reactions	9	9	Single correctCalculation	1
Degree of Dissociationdegree of dissociation from kp	5	5	Numerical valueCalculation	3
Kp for PCl5 Dissociation Type Reactionskp expression from extent of dissociation	4	4	Single correctApplication	1
Kc and Kp Relationshipkc from kp	4	4	Numerical valueCalculation	3
Kp Expression via Partial Pressureskp from equal molecules of reactants and product	4	4	Numerical valueCalculation	2
ICE Table Constructionequilibrium concentration from kc	4	4	Numerical valueCalculation	4
Dalton's Law in Kp Calculationspartial pressure from kc and inert gas	3	3	Numerical valueMulti-step	2
Standard Gibbs Free Energy and Equilibrium Constantstandard gibbs energy from dissociation	3	3	Numerical valueCalculation	3
Heterogeneous Equilibriumpartial pressure from coupled equilibria	2	2	Numerical valueCalculation	2
Kc Expressionwrite kc expression for reaction	2	2	Single correctData or graph	–
Le Chatelier's Principlenew equilibrium concentration after adding reactant	2	2	Numerical valueApplication	1
Temperature Dependence of K (Van 't Hoff Equation)enthalpy from equilibrium constant data	1	1	Numerical valueData or graph	1
Effect of Catalyst on Equilibriumstatement i/ii on catalyst and equilibrium	1	1	Two statementsConceptual	–
Inert Gas Effect at Constant Pressureeffect of inert gas on equilibrium	1	1	Single correctApplication	–
Adding Pure Solid or Liquidle chatelier effect of adding pure solid	1	1	Single correctConceptual	–
Equilibrium Constant from Rate Constantsequilibrium constant from forward and backward rate terms of rate law	1	1	Numerical valueCalculation	1
Rate-Time Graph Analysisgraph interpretation of rate vs time at equilibrium	1	1	Diagram basedData or graph	–

Times and shifts count every analysed shift. Across JEE Main, 78% of questions since 2024 went back to an idea an earlier year had asked; the rest were new. All repeated ideas

Every question

Chemical Equilibrium questions, year by year

The newest 40 show their opening words as they appeared in the official paper; older ones name the idea they tested. Open one for its options and the official answer.

Questions from the official JEE Main Paper 1 shifts published by NTA (CBSE for 2017). Questions NTA dropped are left out. Topic and idea tags, counts and notes are Lumi’s.

Key findings

Questions a shift, year by year

Difficulty, format and skill

Difficulty

Format

Skill tested

New idea, or one asked before?

Coverage of the topic

Chapter, idea, question

Every idea inside this topic

Chemical Equilibrium questions, year by year

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JEE Main 20255 questions in 4 shifts

JEE Main 20248 questions in 8 shifts

JEE Main 20235 questions in 5 shifts

JEE Main 20229 questions in 9 shifts

JEE Main 20219 questions in 8 shifts

JEE Main 20205 questions in 5 shifts

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