JEE Main · Chemistry · Coordination Compounds

Coordination Isomerism: JEE Main previous year questions

Name: Coordination Isomerism: JEE Main previous year questions
Creator: Lumi

39 questions in the 108 JEE Main shifts Lumi analysed, in 8 of 8 years. Pattern: Asked most years. 12 came in 2024–26. Here is how it is asked and which ideas come back.

Questions: 39; in 36 of 108 shifts
Years asked: 8/8; last asked 2026
Chance in a shift: 47%; calibrated model, how we compute it
Weighted estimate: 0.4; model; history: 0.4 a shift on average, typically 0.2–0.8

Key findings

01
Asked in 8 of 8 years with analysed shifts and in 36 of 108 shifts: 39 questions, #86 of 196 topics. It came in every year with analysed shifts.
02
53% of its questions since 2020 tested an idea no earlier year had asked; 12 repeated an idea from the year before.
03
The most repeated idea is Precipitation Tests for Ionization Isomers, asked 8 times in 8 shifts (2017, 2020, 2021, 2022, 2023, 2025, 2026), most often as “moles of precipitate from complex”.
04
JEE Main has asked 20 of the 54 ideas in this topic; 26 have never been asked, directly or inside another question.
05
Mostly asked as single correct (46%); 41% need a numerical answer, 31% are easy and 10% hard.
06
The skill tested most is application (36%), then multi-step (28%).

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: 1 in 1 shift · 2020: 9 in 12 shifts · 2021: 7 in 24 shifts · 2022: 4 in 24 shifts · 2023: 6 in 12 shifts · 2024: 4 in 18 shifts · 2025: 4 in 8 shifts · 2026: 4 in 9 shifts.

Up to 2023: 0.5; a shift, of 25
Since 2024: 0.4; -0.1
Usual gap: 1.3 yrs; between years asking it
Shifts with it: 36/108; 33% of analysed shifts

How it is asked

Difficulty, format and skill

Across all 39 questions on Coordination Isomerism since 2017.

Difficulty

QUESTIONS

12234

Easy12 · 31%
Medium23 · 59%
Hard4 · 10%

Format

Single correct · 18 Q46%
Numerical value · 16 Q41%
Other · 1 Q3%
Two statements · 1 Q3%
Diagram based · 1 Q3%
Assertion–reason · 1 Q3%
Match the list · 1 Q3%

Skill tested

Application · 14 Q36%
Multi-step · 11 Q28%
Conceptual · 5 Q13%
Calculation · 4 Q10%
Recall · 4 Q10%
Diagram reading · 1 Q3%

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 20 of the 54 ideas in this topic. 26 have never been asked yet.

20826

Asked directly20 · 37%
Touched inside another question8 · 15%
Never asked26 · 48%

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

Idea, year, question

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

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

OpenRepeated8 · 21%21%7/82
- 6 Apr ’26 S2 · Q71
  An excess of $\mathrm{AgNO_3}$ is added to 100 mL of a 0.05 M solution of tetraaquadichloridochromium (III) chloride. The number of moles…
  easyNumerical valueAsked the year before
- 7 Apr ’25 S1 · Q62
  An octahedral complex having molecular composition $\mathrm{Co.5NH_3.Cl.SO_4}$ has two isomers A and B. The solution of A gives a white…
  easySingle correct
- 15 Apr ’23 S1 · Q81
  The volume (in mL) of 0.1 M $\mathrm{AgNO_3}$ required for complete precipitation of chloride ions present in 20 mL of 0.01 M solution of…
  mediumNumerical valueAsked the year before
- 29 Jun ’22 S2 · Q87
  For the reaction given below : $\mathrm{CoCl_3\cdot}\,x\,\mathrm{NH_3 + AgNO_3}$ (aq) → If two equivalents of AgCl precipitate out, then…
  easyNumerical valueAsked the year before
- 30 Jun ’22 S1 · Q71
  Correct formula of the compound which gives a white precipitate with $\mathrm{BaCl_2}$ solution, but not with $\mathrm{AgNO_3}$ solution, is
  easySingle correctAsked the year before
- 3 Aug ’21 S1 · Q59
  The number of ions produced in an aqueous solution from the octahedral complex with stoichiometry $\mathrm{CoCl_3.5H_2O}$ , is ________.
  mediumNumerical valueAsked the year before
- 8 Jan ’20 S1 · Q49
  Read the question
  mediumNumerical valueAsked the year before
- 2017 · Q50
  Read the question
  mediumSingle correctNew idea
OpenRepeated4 · 10%10%3/82
OpenRepeated3 · 8%8%3/8
OpenRepeated3 · 8%8%3/8
OpenRepeated3 · 8%8%3/8
OpenRepeated2 · 5%5%2/8
OpenRepeated2 · 5%5%2/8
Open2 · 5%5%1/82
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%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

20 different ideas were tested; 8 came more than once.

Precipitation Tests for Ionization Isomers8×
moles of precipitate from complex
Numerical value · 8 shifts · 5 numerical
Ambidentate Ligands in Linkage Isomerism4×
odd-one-out among ligand sets
Numerical value · 4 shifts · 3 numerical
Facial and Meridional Isomerism in MA3B33×
geometrical isomers of complex from clues
Single correct · 3 shifts · 1 numerical
Square Planar Geometry3×
identify correct geometrical structures of complexes
Single correct · 3 shifts
Total Isomer Calculation3×
count stereoisomers of chelate complex
Numerical value · 3 shifts · 2 numerical
Ambidentate Ligands in Linkage Isomerism2×
identify correct statements on coordination compounds
Other · 2 shifts
Octahedral Geometrical2×
statement i/ii on coordination compound isomerism
Single correct · 2 shifts
Optical Activity in M(AA)2B2 Complexes2×
count complexes showing optical isomerism
Assertion–reason · 2 shifts · 1 numerical
Identifying Coordination Isomerism1×
identify complexes showing a type of isomerism
Single correct · 1 shift
Water Loss and Molar Conductivity in Hydrate Isomers1×
mole ratio from precipitation of complex ions
Numerical value · 1 shift · 1 numerical
Optical Isomerism in Chelates1×
optical isomers of deduced complex
Numerical value · 1 shift · 1 numerical
Optical Isomerism in Tetrahedral Complexes1×
geometrical isomers of tetrahedral complex
Single correct · 1 shift
Chemical Tests for Ionization Isomers1×
ionisable chlorides from precipitation data
Numerical value · 1 shift · 1 numerical
Enantiomers of Tris-Chelate M(AA)3 Complexes1×
optical isomers of complex
Numerical value · 1 shift · 1 numerical
Structural Isomerism Types1×
match list on types of isomerism in complexes
Match the list · 1 shift
Absence of Geometrical Isomerism in Tetrahedral Complexes1×
complex not showing isomerism
Single correct · 1 shift
Dehydration of Hydrate Isomers1×
hydrate isomer formula from mass loss
Single correct · 1 shift
Geometrical Isomerism in MA4B2 Octahedral Complexes1×
identify isomer with given bond angle
Single correct · 1 shift
Optical Activity of Cis-M(AA)2B21×
complex showing optical activity
Single correct · 1 shift
Square Planar MABCD Geometrical Isomers1×
magnetic moment and cfse of complex from isomer count
Single correct · 1 shift

Idea	Times	Shifts	Format	Numerical
Precipitation Tests for Ionization Isomersmoles of precipitate from complex	8	8	Numerical valueApplication	5
Ambidentate Ligands in Linkage Isomerismodd-one-out among ligand sets	4	4	Numerical valueRecall	3
Facial and Meridional Isomerism in MA3B3geometrical isomers of complex from clues	3	3	Single correctApplication	1
Square Planar Geometryidentify correct geometrical structures of complexes	3	3	Single correctApplication	–
Total Isomer Calculationcount stereoisomers of chelate complex	3	3	Numerical valueMulti-step	2
Ambidentate Ligands in Linkage Isomerismidentify correct statements on coordination compounds	2	2	OtherApplication	–
Octahedral Geometricalstatement i/ii on coordination compound isomerism	2	2	Single correctApplication	–
Optical Activity in M(AA)2B2 Complexescount complexes showing optical isomerism	2	2	Assertion–reasonApplication	1
Identifying Coordination Isomerismidentify complexes showing a type of isomerism	1	1	Single correctApplication	–
Water Loss and Molar Conductivity in Hydrate Isomersmole ratio from precipitation of complex ions	1	1	Numerical valueMulti-step	1
Optical Isomerism in Chelatesoptical isomers of deduced complex	1	1	Numerical valueMulti-step	1
Optical Isomerism in Tetrahedral Complexesgeometrical isomers of tetrahedral complex	1	1	Single correctConceptual	–
Chemical Tests for Ionization Isomersionisable chlorides from precipitation data	1	1	Numerical valueMulti-step	1
Enantiomers of Tris-Chelate M(AA)3 Complexesoptical isomers of complex	1	1	Numerical valueApplication	1
Structural Isomerism Typesmatch list on types of isomerism in complexes	1	1	Match the listRecall	–
Absence of Geometrical Isomerism in Tetrahedral Complexescomplex not showing isomerism	1	1	Single correctApplication	–
Dehydration of Hydrate Isomershydrate isomer formula from mass loss	1	1	Single correctCalculation	–
Geometrical Isomerism in MA4B2 Octahedral Complexesidentify isomer with given bond angle	1	1	Single correctConceptual	–
Optical Activity of Cis-M(AA)2B2complex showing optical activity	1	1	Single correctApplication	–
Square Planar MABCD Geometrical Isomersmagnetic moment and cfse of complex from isomer count	1	1	Single correctMulti-step	–

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

Coordination Isomerism questions, year by year

The opening words of each question as it appeared in the official paper, with the idea it 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

Idea, year, question

Every idea inside this topic

Coordination Isomerism questions, year by year

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JEE Main 20254 questions in 4 shifts

JEE Main 20244 questions in 3 shifts

JEE Main 20236 questions in 5 shifts

JEE Main 20224 questions in 4 shifts

JEE Main 20217 questions in 7 shifts

JEE Main 20209 questions in 8 shifts

JEE Main 20171 question in 1 shift

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