Mole Concept & Stoichiometry · JEE Main previous year questions

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2026 29 questions

Q512026 · 6 Apr 2026 · Shift 1
An oxide of iron contains $69.9%$ iron, its empirical formula, is: (Given : Molar mass of $Fe$ and $O$ are $56$ and $16 g mo l^{- 1}$ respectively.)
1. A. $FeO$
2. B. $F e_{2} O_{3}$
3. C. $F e_{3} O_{4}$
4. D. $Fe O_{3}$
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Answer: B
Q562026 · 6 Apr 2026 · Shift 1
When $0.25 moles$ of a non-volatile, non-ionizable solute was dissolved in $1 mole$ of a solvent the vapor pressure of solution was $x %$ of vapor pressure of pure solvent. What is $x %$ ?
1. A.50%
2. B.60%
3. C.70%
4. D.80%
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Answer: D
Q732026 · 6 Apr 2026 · Shift 1· Numerical answer
$4.7 g$ of phenol is heated with $Zn$ to give product X. If this reaction goes to $60%$ completion then the number of moles of compound X formed will be ____ $\times 1 0^{- 2}$ .(Nearest Integer) (Given molar mass in $g mo l^{- 1}$ : H:1, C:12, O:16)
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Answer: 3
Q712026 · 6 Apr 2026 · Shift 2· Numerical answer
An excess of $AgNO_{3}$ is added to $100 mL$ of a $0.05 M$ solution of tetraaquadichloridochromium(III) chloride. The number of moles of $AgCl$ precipitated will be ________ $\times 1 0^{- 3}$ . (Nearest integer)
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Answer: 5
Q722026 · 6 Apr 2026 · Shift 2· Numerical answer
An alkane $(Y)$ requires $8 moles$ of oxygen for complete combustion and on chlorination with $Cl_{2} / h ν$ , $(Y)$ gives only one monochlorinated product $(Z)$ . The total number of primary carbon atoms in $(Y)$ is ________.
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Answer: 4
Q542026 · 5 Apr 2026 · Shift 1
What is the mole fraction of water in $10%$ by weight (w/w) of aqueous urea solution? [Given: Molar mass of $H$ , $O$ , $C$ and $N$ are $1$ , $16$ , $12$ and $14 g mol^{- 1}$ respectively.]
1. A. $0.825$
2. B. $0.032$
3. C. $0.867$
4. D. $0.967$
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Answer: D
Q732026 · 5 Apr 2026 · Shift 1· Numerical answer
One mole of phenol is treated with dilute $HNO_{3}$ at $298 K$ to give a mixture of products. The mixture is separated by steam distillation. The steam volatile compound (X) is separated. The increase in percentage of oxygen in (X) with respect to phenol is _______ $\times 1 0^{- 1} %$ (Given molar mass in $g mol^{- 1}$ $H:1$ , $C:12$ , $N:14$ , $O:16$ )
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Answer: 175
Q512026 · 4 Apr 2026 · Shift 1
Number of moles and number of molecules in $1.4187 L$ of $S O_{2}$ at STP respectively are
1. A. $0.1266$ ; $3.812 \times 1 0^{22}$
2. B. $0.0633$ ; $3.812 \times 1 0^{22}$
3. C. $0.1266$ ; $7.6238 \times 1 0^{22}$
4. D. $0.0633$ ; $7.6238 \times 1 0^{22}$
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Answer: B
Q562026 · 4 Apr 2026 · Shift 1
In order to oxidise a mixture of $1 mole$ each of $Fe C_{2} O_{4}$ , $F e_{2} (C_{2} O_{4})_{3}$ , $FeS O_{4}$ and $F e_{2} (S O_{4})_{3}$ in acidic medium, the number of moles of $KMn O_{4}$ required is
1. A.3
2. B.2
3. C.5
4. D.7
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Answer: B
Q732026 · 4 Apr 2026 · Shift 1· Numerical answer
$2.0 g$ 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 $g mo l^{- 1}$ $H : 1$ , $C : 12$ , $Br : 80$ , $Ag : 108$ )
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Answer: 5
Q512026 · 4 Apr 2026 · Shift 2
The correct order of total number of atoms present in (A) $2 moles$ of cyclohexane (B) $684 g$ of sucrose (C) $90.8 L$ of dihydrogen at STP is:
1. A.C > A > B
2. B.C > B > A
3. C.B > C > A
4. D.B > A > C
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Answer: D
Q562026 · 2 Apr 2026 · Shift 1
The solubility product constants of $A g_{2} Cr O_{4}$ and $AgBr$ are $32 x$ and $4 y$ respectively at $298 K$ . The value of $(\frac{molarity of A g _{2} Cr O _{4}}{molarity of AgBr})$ can be expressed as :
1. A. $\frac{2 3 x}{y}$
2. B. $2 \frac{x}{y}$
3. C. $\frac{x}{y}$
4. D. $\frac{3 x}{y}$
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Answer: D
Q712026 · 2 Apr 2026 · Shift 1· Numerical answer
$5.33 g$ of $CrC l_{3} \cdot 6 H_{2} O$ , which is a $1 : 3$ electrolyte, is dissolved in water and is passed through a cation exchanger. The chloride ions in the eluted solution, on treatment with $AgN O_{3}$ results in $8.61 g$ of $AgCl$ . The ratio of moles of complex reacted and moles of $AgCl$ formed is ____ $\times 1 0^{- 2}$ . (Nearest integer) $[Molar mass in g mo l^{- 1} Cr : 52, Ag : 108, Cl : 35.5, H : 1, O : 16]$
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Answer: 33
Q722026 · 2 Apr 2026 · Shift 1· Numerical answer
Consider the isomers of hydrocarbon with molecular formula $C_{5} H_{10}$ . These isomers do not decolourise $KMn O_{4}$ solution. These isomers are subjected to chlorination with chlorine in presence of light to give monochloro compounds. The total number of monochloro compounds (structural isomers only) formed is ____.
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Answer: 14
Q732026 · 2 Apr 2026 · Shift 1· Numerical answer
One mole of an alkane (x) requires 8 mole oxygen for complete combustion. Sum of number of carbon and hydrogen atoms in the alkane (x) is ____.
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Answer: 17
Q512026 · 2 Apr 2026 · Shift 2
The ratio of mass percentage (w/w) of $C : H$ in a hydrocarbon is $12 : 1$ . It has two carbon atoms. The weight (in g) of $C O_{2} (g)$ formed when $3.38 g$ of this hydrocarbon is completely burnt in oxygen is : (Given : Molar mass in $g mo l^{- 1}$ $C : 12$ , $H : 1$ , , $O : 16$ )
1. A.5.68
2. B.11.44
3. C.22.74
4. D.17.05
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Answer: B
Q562026 · 28 Jan 2026 · Shift 1
1. A.Statement I is true but Statement II is false
2. B.Both Statement I and Statement II are true
3. C.Statement I is false but Statement II is true
4. D.Both Statement I and Statement II are false
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Answer: B
Q602026 · 28 Jan 2026 · Shift 1
At $T (K)$ , $2 moles$ of liquid A and $3 moles$ of liquid B are mixed. The vapour pressure of ideal solution formed is $320 mm Hg$ . At this stage, one mole of A and one mole of B are added to the solution. The vapour pressure is now measured as $328.6 mm Hg$ . The vapour pressure (in $mm Hg$ ) of A and B are respectively:
1. A.400, 300
2. B.600, 400
3. C.500, 200
4. D.300, 200
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Answer: C
Q632026 · 28 Jan 2026 · Shift 2
Observe the following equilibrium in a 1 L flask. A(g) ⇌ B(g) At T(K), the equilibrium concentrations of A and B are 0.5 M and 0.375 M respectively. 0.1 moles of A is added into the flask and heated to T(K) to establish the equilibrium again. The new equilibrium concentrations (in M) of A and B are respectively
1. A.0.742, 0.557.
2. B.0.367, 0.275.
3. C.0.53, 0.4.
4. D.0.557, 0.418.
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Answer: D
Q522026 · 23 Jan 2026 · Shift 1
1. A.
2. B.
3. C.
4. D.
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Answer: A
Q552026 · 23 Jan 2026 · Shift 1
' $x$ ' is the product which is obtained from propanenitrile and stannous chloride in the presence of hydrochloric acid followed by hydrolysis. ' $y$ ' is the product which is obtained from the but-2-ene by the ozonolysis followed by hydrolysis. From the following, which product is not obtained when one mole of ' $x$ ' and one mole of ' $y$ ' react with each other in the presence of alkali followed by heating?
1. A.2-Methylpent-2-enal
2. B.2-Methylbut-2-enal
3. C.3-Methylbut-2-enal
4. D.Pent-2-enal
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Answer: C
Q652026 · 23 Jan 2026 · Shift 2
A student has been given a compound " $x$ " of molecular formula- $C_{6} H_{7} N$ . ' $x$ ' is sparingly soluble in water. However, on addition of dilute mineral acid, ' $x$ ' becomes soluble in water. ' $x$ ' when treated with $CHCl_{3}$ and $KOH(alc)$ , ' $y$ ' is produced. ' $y$ ' has a specific unpleasant smell. On treatment with benzenesulphonyl chloride, ' $x$ ' gives a compound ' $z$ ' which is soluble in alkali. The number of different " H " atoms present in ' z ' is:-
1. A.8
2. B.4
3. C.5
4. D.7
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Answer: D
Q742026 · 23 Jan 2026 · Shift 2· Numerical answer
$X_{2} (g) + Y_{2} (g) ⇌ 2 Z (g)$ $X_{2} (g)$ and $Y_{2} (g)$ are added to a 1 L flask and it is found that the system attains the above equilibrium at $T (K)$ with the number of moles of $X_{2} (g), Y_{2} (g)$ and $Z (g)$ being 3,3 and 9 mol respectively (equilibrium moles). Under this condition of equilibrium, 10 mol of $Z (g)$ is added to the flask and the temperature is maintained at $T (K)$ . Then the number of moles of $Z (g)$ in the flask when the new equilibrium is established is _____. (Nearest integer)
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Answer: 15
Q622026 · 22 Jan 2026 · Shift 1
1. A.
2. B.
3. C.
4. D.
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Answer: C
Q722026 · 22 Jan 2026 · Shift 1· Numerical answer
The cycloalkene $(X)$ on bromination consumes one mole of bromine per mole of $(X)$ and gives the product $(Y)$ in which $C : Br$ ratio is 3:1. The percentage of bromine in the product $(Y)$ is ____ %. (Nearest integer) (Given : molar mass in $g mo l^{- 1}$ $H : 1, C : 12, O : 16, Br : 80$ )
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Answer: 66