JEE MAIN - Chemistry (2025 - 28th January Morning Shift)

1
The incorrect decreasing order of atomic radii is
Answer
(D)
$\mathrm{Be}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Si}$
2
What is the freezing point depression constant of a solvent, 50 g of which contain 1 g non volatile solute (molar mass $256 \mathrm{~g} \mathrm{~mol}^{-1}$ ) and the decrease in freezing point is 0.40 K ?
Answer
(C)
$5.12 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$
3

Given below are two statements:

Statement I : D-glucose pentaacetate reacts with 2,4 -dinitrophenylhydrazine

Statement II : Starch, on heating with concentrated sulfuric acid at $100^{\circ} \mathrm{C}$ and $2-3 \mathrm{atmosphere}$ pressure produces glucose.

In the light of the above statements, choose the correct answer from the options given below

Answer
(C)
Statement I is false but Statement II is true
4
A weak acid HA has degree of dissociation x . Which option gives the correct expression of ( pH - $\mathrm{pK}_{\mathrm{a}}$)?
Answer
(D)
$\log \left(\frac{x}{1-x}\right)$
5

JEE Main 2025 (Online) 28th January Morning Shift Chemistry - Chemical Kinetics and Nuclear Chemistry Question 1 English

For a given reaction $\mathrm{R} \rightarrow \mathrm{P}, \mathrm{t}_{1 / 2}$ is related to $[\mathrm{A}]_0$ as given in table.

Given: $\log 2=0.30$

Which of the following is true?

A. The order of the reaction is $1 / 2$.

B. If $[\mathrm{A}]_0$ is 1 M , then $\mathrm{t}_{1 / 2}$ is $200 \sqrt{10} \mathrm{~min}$

C. The order of the reaction changes to 1 if the concentration of reactant changes from 0.100 M to 0.500 M.

D. $\mathrm{t}_{1 / 2}$ is 800 min for $[\mathrm{A}]_0=1.6 \mathrm{M}$

Choose the correct answer from the options given below:

Answer
(B)
A, B and D Only
6

A molecule ("P") on treatment with acid undergoes rearrangement and gives ("Q"). ("Q") on ozonolysis followed by reflux under alkaline condition gives (" $R$ "). The structure of (" $R$ ") is given below.

JEE Main 2025 (Online) 28th January Morning Shift Chemistry - Aldehydes, Ketones and Carboxylic Acids Question 2 English

The structure of ("P") is

Answer
A
D
7

The products A and B in the following reactions, respectively are

$\mathrm{A} \stackrel{\mathrm{Ag}-\mathrm{NO}_2}{\longleftrightarrow} \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{Br} \xrightarrow{\mathrm{AgCN}} \mathrm{B}$

Answer
(D)
$\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{NO}_2, \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{NC}$
8

In a multielectron atom, which of the following orbitals described by three quantum numbers will have same energy in absence of electric and magnetic fields?

A. $\mathrm{n}=1, \mathrm{l}=0, \mathrm{~m}_1=0$

B. $\mathrm{n}=2, \mathrm{l}=0, \mathrm{~m}_1=0$

C. $\mathrm{n}=2, \mathrm{I}=1, \mathrm{~m}_1=1$

D. $\mathrm{n}=3, \mathrm{l}=2, \mathrm{~m}_1=1$

E. $\mathrm{n}=3, \mathrm{l}=2, \mathrm{~m}_1=0$

Choose the correct answer from the options given below:

Answer
(D)
D and E Only
9

Given below are two statements:

Statement I: In the oxalic acid vs $\mathrm{KMnO}_4$ (in the presence of dil $\mathrm{H}_2 \mathrm{SO}_4$ ) titration the solution needs to be heated initially to $60^{\circ} \mathrm{C}$, but no heating is required in Ferrous ammonium sulphate (FAS) vs $\mathrm{KMnO}_4$ titration (in the presence of dil $\mathrm{H}_2 \mathrm{SO}_4$)

Statement II: In oxalic acid vs $\mathrm{KMnO}_4$ titration, the initial formation of $\mathrm{MnSO}_4$ takes place at high temperature, which then acts as catalyst for further reaction. In the case of FAS vs $\mathrm{KMnO}_4$, heating oxidizes $\mathrm{Fe}^{2+}$ into $\mathrm{Fe}^{3+}$ by oxygen of air and error may be introduced in the experiment.

In the light of the above statements, choose the correct answer from the options given below

Answer
(C)
Both Statement I and Statement II are true
10
Consider the following elements $\mathrm{In}, \mathrm{Tl}, \mathrm{Al}, \mathrm{Pb}, \mathrm{Sn}$ and Ge . The most stable oxidation states of elements with highest and lowest first ionisation enthalpies, respectively, are
Answer
(A)
+4 and +1
11

Both acetaldehyde and acetone (individually) undergo which of the following reactions?

A. Iodoform Reaction

B. Cannizaro Reaction

C. Aldol Condensation

D. Tollen's Test

E. Clemmensen Reduction

Choose the correct answer from the options given below:

Answer
(C)
A, C and E Only
12

The compounds that produce $\mathrm{CO}_2$ with aqueous $\mathrm{NaHCO}_3$ solution are:

JEE Main 2025 (Online) 28th January Morning Shift Chemistry - Aldehydes, Ketones and Carboxylic Acids Question 1 English

Choose the correct answer from the options given below:

Answer
(D)
A, C and D Only
13
The metal ion whose electronic configuration is not affected by the nature of the ligand and which gives a violet colour in non-luminous flame under hot condition in borax bead test is
Answer
(C)
$\mathrm{Ni}^{2+}$
14

Consider ' n ' is the number of lone pair of electrons present in the equatorial position of the most stable structure of $\mathrm{ClF}_3$. The ions from the following with ' n ' number of unpaired electrons are

A. $\mathrm{V}^{3+}$

B. $\mathrm{Ti}^{3+}$

C. $\mathrm{Cu}^{2+}$

D. $\mathrm{Ni}^{2+}$

E. $\mathrm{Ti}^{2+}$

Choose the correct answer from the options given below:

Answer
(B)
A, D and E Only
15

The correct order of stability of following carbocations is :

JEE Main 2025 (Online) 28th January Morning Shift Chemistry - Basics of Organic Chemistry Question 1 English

Answer
(D)
C > A > B > D
16

Match the List - I with List - II

List - I
(Redox Reaction)
List - II
(Type of Redox Reaction)
(A) $\begin{aligned} & \mathrm{CH}_{4(\mathrm{~g})}+2 \mathrm{O}_{2(\mathrm{~g})} \xrightarrow{\Delta} \mathrm{CO}_{2(\mathrm{~g})} \\ & +2 \mathrm{H}_2 \mathrm{O}_{(\mathrm{l})}\end{aligned}$ (I) Disproportionation reaction
(B) $2 \mathrm{NaH}_{(\mathrm{s})} \xrightarrow{\Delta} 2 \mathrm{Na}_{(\mathrm{s})}+\mathrm{H}_{2(\mathrm{~g})}$ (II) Combination reaction
(C) $\begin{aligned} & \mathrm{V}_2 \mathrm{O}_{5(\mathrm{~s})}+5 \mathrm{Ca}_{(\mathrm{s})} \xrightarrow{\Delta} 2 \mathrm{~V}_{(\mathrm{s})} \\ & +5 \mathrm{CaO}_{(\mathrm{s})}\end{aligned}$ (III) Decomposition reaction
(D) $\begin{aligned} & 2 \mathrm{H}_2 \mathrm{O}_{2(\mathrm{aq})} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{H}_2 \mathrm{O}_{(\mathrm{l})}+ \\ & \mathrm{O}_{2(\mathrm{~g})}\end{aligned}$ (IV) Displacement reaction

Choose the correct answer from the options given below:

Answer
(D)
A-II, B-III, C-IV, D-I
17

Given below are two statements :

Statement I : JEE Main 2025 (Online) 28th January Morning Shift Chemistry - Alcohols, Phenols and Ethers Question 1 English 1

Statement II : In JEE Main 2025 (Online) 28th January Morning Shift Chemistry - Alcohols, Phenols and Ethers Question 1 English 2, intramolecular substitution takes place first by involving lone pair of electrons on nitrogen.

In the light of the above statements, choose the most appropriate answer from the options given below

Answer
(A)
Both Statement I and Statement II are correct
18

Which of the following oxidation reactions are carried out by both $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ and $\mathrm{KMnO}_4$ in acidic medium?

A. $\Gamma^{-} \rightarrow \mathrm{I}_2$

B. $\mathrm{S}^{2-} \rightarrow \mathrm{S}$

C. $\mathrm{Fe}^{2+} \rightarrow \mathrm{Fe}^{3+}$

D. $\mathrm{I}^{-} \rightarrow \mathrm{IO}_3^{-}$

E. $\mathrm{S}_2 \mathrm{O}_3{ }^{2-} \rightarrow \mathrm{SO}_4^{2-}$

Choose the correct answer from the options given below :

Answer
(A)
A, B and C Only
19
The molecules having square pyramidal geometry are
Answer
(C)
$\mathrm{BrF}_5 ~\&~ \mathrm{XeOF}_4$
20
Ice and water are placed in a closed container at a pressure of 1 atm and temperature 273.15 K . If pressure of the system is increased 2 times, keeping temperature constant, then identify correct observation from following
Answer
(C)
The solid phase (ice) disappears completely.
21
The formation enthalpies, $\Delta \mathrm{H}_{\mathrm{f}}^{\ominus}$ for $\mathrm{H}_{(\mathrm{g})}$ and $\mathrm{O}_{(\mathrm{g})}$ are 220.0 and $250.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$, respectively, at 298.15 K , and $\Delta \mathrm{H}_{\mathrm{f}}^{\ominus}$ for $\mathrm{H}_2 \mathrm{O}_{(\mathrm{g})}$ is $-242.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$ at the same temperature. The average bond enthalpy of the $\mathrm{O}-\mathrm{H}$ bond in water at 298.15 K is _______ $\mathrm{kJ} \mathrm{~mol}^{-1}$ (nearest integer).
Answer
466
22

Consider the following sequence of reactions:

JEE Main 2025 (Online) 28th January Morning Shift Chemistry - Haloalkanes and Haloarenes Question 1 English

11.25 mg of chlorobenzene will produce ___________$\times 10^{-1} \mathrm{mg}$ of product B.

(Consider the reactions result in complete conversion.)

[Given molar mass of $\mathrm{C}, \mathrm{H}, \mathrm{O}, \mathrm{N}$ and Cl as $12,1,16,14$ and $35.5 \mathrm{~g} \mathrm{~mol}^{-1}$ respectively]

Answer
93
23

The molarity of a $70 \%$ (mass/mass) aqueous solution of a monobasic acid (X) is _________ $\times 10^{-1}$ M (Nearest integer)

[Given: Density of aqueous solution of (X) is $1.25 \mathrm{~g} \mathrm{~mL}^{-1}$

Molar mass of the acid is $70 \mathrm{~g} \mathrm{~mol}^{-1}$ ]

Answer
125
24

Given below is the plot of the molar conductivity vs $\sqrt{\text { concentration }}$ for KCl in aqueous solution.

JEE Main 2025 (Online) 28th January Morning Shift Chemistry - Electrochemistry Question 1 English

If, for the higher concentration of KCl solution, the resistance of the conductivity cell is $100 \Omega$, then the resistance of the same cell with the dilute solution is ' x ' $\Omega$

The value of $x$ is _________ (Nearest integer)

Answer
150
25

Quantitative analysis of an organic compound (X) shows following % composition.

C : $14.5 \%$

Cl : 64.46%

H: 1.8 %

(Empirical formula mass of the compound $(\mathrm{X})$ is _________ $\times 10^{-1}$

(Given molar mass in $\mathrm{g} \mathrm{~mol}^{-1}$ of $\mathrm{C}: 12, \mathrm{H}: 1, \mathrm{O}: 16, \mathrm{Cl}: 35.5$)

Answer
1655