Purification & Characterisation

20 JEE Main questions · Chemistry

ChemistryJEE Main 21 Jan 2026, Shift 1·Q8·MCQ·Easy–moderate
Open
Carius method sulphur estimation
In Carius method, 0.75 g of an organic compound gave 1.2 g of barium sulphate, find percentage of sulphur (molar mass 32 g mol $^{-1}$ ). Molar mass of barium sulphate is 233 g mol $^{-1}$ .
1. (1)4.55%
2. (2)10.30%
3. (3)21.97%
4. (4)16.48%
ChemistryJEE Main 21 Jan 2026, Shift 2·Q5·MCQ·Easy–moderate
Open
Phosphorus estimation as pyrophosphate
By usual analysis, 1.00g of compound (X) gave 1.79g of magnesium pyrophosphate. The percentage of phosphorus in compound (X) is: (nearest integer)
(Given, molar mass in g mol $^{-1}$ : O $= 16$ , Mg $= 24$ , P $= 31$ )
1. (1)50
2. (2)30
3. (3)20
4. (4)40
ChemistryJEE Main 22 Jan 2026, Shift 1·Q24·Numerical·Easy–moderate
Open
Carius method halogen estimation
Sodium fusion extract of an organic compound (Y) with $\ce{CHCl3}$ and chlorine water gives violet color to the $\ce{CHCl3}$ layer. 0.15g of (Y) gave 0.12 g of the silver halide precipitate in Carius method. Percentage of halogen in the compound (Y) is . (Nearest integer).
(Given : molar mass g mol $^{-1}$ C : 12, H : 1, Cl : 35.5, Br : 80, I : 127)
ChemistryJEE Main 22 Jan 2026, Shift 2·Q6·MCQ·Easy–moderate
Open
Kjeldahl method nitrogen estimation
When 1 g of compound (X) is subjected to Kjeldahl's method for estimation of nitrogen, 15 mL, 1M $\ce{H2SO4}$ was neutralized by ammonia evolved. The percentage of nitrogen in compound (X) is :
1. (1)21
2. (2)0.42
3. (3)42
4. (4)0.21
ChemistryJEE Main 23 Jan 2026, Shift 1·Q17·MCQ·Easy
Open
Sublimation and boiling point
Given below are two statements :
Statement-I : Sublimation is used for the separation and purification of compounds with low melting point.
Statement-II : The boiling point of a liquid increases as the external pressure is reduced.
In the light of the above statements, choose the correct answer from the options given below :
1. (1)Statement-I is false but Statement-II is true.
2. (2)Statement-I is true but Statement-II is false.
3. (3)Both Statement-I and Statement-II are true.
4. (4)Both Statement-I and Statement-II are false.
ChemistryJEE Main 23 Jan 2026, Shift 2·Q15·MCQ·Easy–moderate
Open
Carius method halogen estimation
In Carius method 0.2425 g of an organic compound gave 0.5253 g silver chloride. The percentage of chlorine in the organic compound is
1. (1)53.58%
2. (2)87.65%
3. (3)37.57%
4. (4)34.79%
We corrected a printing error in the original paper
Source printed “0.2425 g of an organic compounds”.
ChemistryJEE Main 24 Jan 2026, Shift 1·Q24·Numerical·Easy–moderate
Open
Dumas method nitrogen estimation
In Dumas method for estimation of nitrogen, 0.50 g of an organic compound gave 70 mL of nitrogen collected at 300 K and 715 mm pressure. The percentage of nitrogen in the organic compound is %
(Aqueous tension at 300 K is 15 mm).
ChemistryJEE Main 24 Jan 2026, Shift 2·Q21·Numerical·Easy–moderate
Open
Carbon hydrogen estimation
0.25 g of an organic compound “A” containing carbon, hydrogen and oxygen was analysed using the combustion method. There was an increase in mass of $\ce{CaCl2}$ tube and potash tube at the end of the experiment. The amount was found to be 0.15 g and 0.1837 g, respectively. The percentage of oxygen in compound A is %. (Nearest integer)
(Given : molar mass in g mol $^{-1}$ H : 1, C : 12, O : 16)
ChemistryJEE Main 28 Jan 2026, Shift 1·Q5·MCQ·Easy–moderate
Open
Separation of isomeric products
Method used for separation of mixture of products (B and C) obtained in the following reaction is:
1. (1)Simple distillation
2. (2)sublimation
3. (3)steam distillation
4. (4)fractional distillation
ChemistryJEE Main 28 Jan 2026, Shift 1·Q24·Numerical·Moderate
Open
Quantitative estimation of elements
0.53 g of an organic compound (x) when heated with excess of nitric acid (concentrated) and then with silver nitrate gave 0.75 g of silver bromide precipitate. 1.0 g of (x) gave 1.32 g of $\ce{CO2}$ gas on combustion. The percentage of hydrogen in the compound (x) is %. [Nearest Integer]
[Given : Molar mass in g mol $^{-1}$ H : 1, C : 12, Br : 80, Ag : 108, O : 16; Compound (x) : $\ce{C_{x}H_{y}Br_{z}}$ ]
ChemistryJEE Main 28 Jan 2026, Shift 2·Q20·MCQ·Easy
Open
Carius method sulphur estimation
A student has been given 0.314 g of an organic compound and asked to estimate Sulphur. During the experiment, the student has obtained 0.4813 g of barium sulphate. The percentage of sulphur present in the compound is .
(Given Molar mass in g mol $^{-1}$ S:32, $\ce{BaSO4}$ : 233)
1. (1)42.10%
2. (2)63.15%
3. (3)21.05%
4. (4)48.24%
ChemistryJEE Main 2 Apr 2026, Shift 1·Q13·MCQ·Easy–moderate
Open
Distillation methods of purification
Given below are two statements :
Statement (I) : 1,2,3-Trihydroxypropane can be separated from water by simple distillation.
Statement (II) : An azeotropic mixture cannot be separated by fractional distillation.
In the light of the above statements, choose the correct answer from the options given below :
1. (1)Both Statement I and Statement II are true
2. (2)Both Statement I and Statement II are false
3. (3)Statement I is true but Statement II is false
4. (4)Statement I is false but Statement II is true
We corrected a printing error in the original paper
Source printed “An azotropic mixture”.
ChemistryJEE Main 2 Apr 2026, Shift 2·Q12·MCQ·Easy–moderate
Open
Estimation of carbon and hydrogen
Complete combustion of X g of an organic compound gave 0.25 g of $\ce{CO2}$ and 0.12 g of $\ce{H2O}$ . If the % of carbon is 25% and of hydrogen is 4.89%, then X = $\times10^{-3}$ g. (Nearest integer)
(Molar mass of C, H and O are 12, 1 and 16 g mol $^{-1}$ respectively.)
1. (1)273
2. (2)27
3. (3)2730
4. (4)227
ChemistryJEE Main 4 Apr 2026, Shift 1·Q23·Numerical·Moderate
Open
Carius method empirical formula
2.0 g of a bromo hydrocarbon (X) was subjected to Carius analysis, gave 3.36 g of AgBr. The percentage of carbon in the compound (X) is 26.7%. Total number of carbon atoms in the empirical formula for compound (X) is .
(Given molar mass in g mol $^{-1}$ H : 1, C : 12, Br : 80, Ag : 108)
ChemistryJEE Main 4 Apr 2026, Shift 2·Q25·Numerical·Easy–moderate
Open
Quantitative estimation of sulphur
In sulphur estimation, $2.0\times10^{-3}$ mol of an organic compound (X) (molar mass 76 g mol $^{-1}$ ) gave 0.4813 g of barium sulphate (molar mass 233 g mol $^{-1}$ ). The percentage of sulphur in the compound (X) is $\times\,10^{-1}$ %
(Nearest integer)
ChemistryJEE Main 5 Apr 2026, Shift 1·Q22·Numerical·Easy–moderate
Open
Carius method sulphur estimation
In an estimation of sulphur by Carius method 0.2g of the substance gave 0.6 g of $\ce{BaSO4}$ . The percentage of sulphur in the substance is %.
(Given molar mass in g mol $^{-1}$ S : 32, $\ce{BaSO4}$ : 233)
We corrected a printing error in the original paper
Source printed “BaSO $_4$ : 231” (the molar mass of BaSO $_4$ is 137 + 32 + 64 = 233); corrected to 233. Answer corrected; the source key is 42 (computed with 231) — with 233, $(32/233)\times(0.6/0.2)\times100 = 41.2$ , i.e. 41.

ChemistryJEE Main 5 Apr 2026, Shift 2·Q12·MCQ·Easy

Distillation methods

Match List-I with List-II.

	List-I (Purification technique)		List-II (Used to separate)
A.	Simple distillation	I.	Steam volatile compound
B.	Fractional distillation	II.	Two liquids with large difference in boiling points
C.	Steam distillation	III.	Liquid decomposing at its boiling point
D.	Distillation under reduced pressure	IV.	Two liquids with close boiling points

Choose the correct answer from the options given below :

(1)A-II, B-III, C-I, D-IV
(2)A-II, B-IV, C-I, D-III
(3)A-II, B-IV, C-III, D-I
(4)A-IV, B-III, C-II, D-I

We corrected a printing error in the original paper

Answer corrected; the source key is (3) — steam distillation separates steam-volatile compounds (C-I) and distillation under reduced pressure is used for liquids that decompose at their boiling point (D-III).

ChemistryJEE Main 6 Apr 2026, Shift 1·Q13·MCQ·Easy–moderate
Open
Chromatography rf value and polarity
$R_\mathrm{f}$ value for 2-methylpropene in a solvent system (Ethyl acetate + ether) is 0.42. 2-methylpropene is treated with dilute $\ce{H2SO4}$ to give major organic product (X). $R_\mathrm{f}$ value for (X) in the same solvent system under identical condition will be :
1. (1)0.42
2. (2)0.82
3. (3)0.62
4. (4)0.12
ChemistryJEE Main 6 Apr 2026, Shift 2·Q12·MCQ·Easy
Open
Differential extraction and steam distillation
Given below are two statements :
Statement I : A mixture of $\ce{C12H22O11}$ (sugar) and NaCl can be separated by dissolving sugar in alcohol, due to differential solubility
Statement II : Rose essence from rose petals is separated by steam distillation due to its high volatility and insolubility in $\ce{H2O}$ .
In the light of the above statements, choose the correct answer from the options given below :
1. (1)Both Statement I and Statement II are true
2. (2)Both Statement I and Statement II are false
3. (3)Statement I is true but Statement II is false
4. (4)Statement I is false but Statement II is true
We corrected a printing error in the original paper
Source printed options (3) and (4) as “Statement I is true Statement II is false” and “Statement I is false Statement II is true”.
ChemistryJEE Main 8 Apr 2026, Shift 2·Q12·MCQ·Easy
Open
Fractional distillation
Given below are two statements :
Statement I : Vapours of the liquid with higher boiling point condense before vapours of the liquid with lower boiling points in fractional distillation.
Statement II : The vapours rising up in the fractionating column become richer in high boiling component of the mixture.
In the light of the above statements, choose the correct answer from the option given below :
1. (1)Both Statement I and Statement II are true
2. (2)Both Statement I and Statement II are false
3. (3)Statement I is true but Statement II are false
4. (4)Statement I is false but Statement II are true