Most Difficult Questions in JEE Main covers organic and inorganic chemistry, electrostatics, mechanics, differential equations, thermodynamics, optics, etc. Candidates must practise these topics and other physics, chemistry and mathematics chapters to gain good scores in the JEE main exam. 

Further, they must understand the JEE main syllabus thoroughly along with the JEE main exam pattern for a better understanding of the question paper for each subject.

Also Check: How to Apply for Colleges After JEE Main 2025?

Top 9 Most Difficult Questions in JEE Main

In the JEE Main syllabus there are numerous chapters and each chapter has concepts that are important for the examinees. Yet, there are some sets of questions that are the most difficult questions in the JEE main exam paper. 

Students can go through the most difficult questions in JEE Main given below.

Q1. If the sum of the first ten terms of the series is (13/5) + (13/5) + (13/5) + 4 + (13/5) +…, is (16/5)m, then m is equal to:

1. 99
2. 102
3. 101
4. 100

Ans. 101

Also Check: JEE Main Model Questions with Solutions

Q2. For x∈R, f(x) = |log2 – sinx| and g(x) = f(f(x)), then:

1. g is differentiable at x = 0 and g'(0) = –sin(log2)
2. g is not differentiable at x = 0
3. g'(0) = cos(log2)
4. g'(0) = –cos(log2)

Ans. g'(0) = cos(log2)

Also Check:  JEE Main Model Questions with Solutions - Download PDF

Q3. If a curve y = f(x) passes through the point (1, –1) and fulfill the given differential equation, y(1 + xy) dx = x dy, then f(-1/2) is equal to:

1. 4/5
2. -2/5
3. -4/5
4. 2/5

Ans. ⅘

Also Read: JJEE Main MCQ Questions with Solutions

Q4. The pair having the same magnetic moment is: [At. No.: Cr = 24, Mn = 25, Fe = 26, Co = 27]

1. [Cr(H2O)6]2+ and [Fe(H2O)6]2+
2. [Mn(H2O)6]2+ and [Cr(H2O)6]2+
3. [CoCl4]2– and [Fe(H2O)6]2+
4. [Cr(H2O)6]2+ and [CoCl4]2–

Ans. [Cr(H2O)6]2+ and [Fe(H2O)6]2+

Also Read: JEE Mains Differentiation Questions with Answers

Q5. A wire of length two units is cut into two parts, bent respectively, to form a square of side = x units and a circle of radius = r units. If the sum of the areas of the square and the circle so formed is minimum, then:

1. (4-π)x = πr
2. x = 2r
3. 2x = r
4. 2x = (π + 4)r

Ans. 2r

Also Check: JEE Main Important Formulas 2025 - Subject Wise PDF Download

Q6. Which one of the following complexes shows optical isomerism?

1. cis[Co(en)2Cl2]Cl
2. trans[Co(en)2Cl2]Cl
3. [Co(NH3)4Cl2]Cl
4. [Co(NH3)3Cl3] (en = ethylenediamine)

Ans. (cis[Co(en)2Cl2]Cl

Also Check: JEE Main Model Questions with Solutions - Download PDF

Q7. The region between two concentric spheres of radii ‘a’ and ‘b’ has volume charge density ρ=A/r, where A is a constant and r is the distance from the centre. At the centre of the spheres is a point charge Q. The value of A, such that the electric field in the region between the spheres will be constant, is:

1. Q/[2π(b2-a2)]
2. 2Q/[π(b2-a2)]
3. 2Q/πa2
4. Q/2πa2

Ans. Q/2πa2

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Q8. The decomposition of H2O2 follows a first-order reaction. In fifty minutes, the concentration of H2O2 decreases from 0.5 to 0.125 M in one such decomposition. When the concentration of H2O2 reaches 0.05 M, the rate of formation of O2 will be:

1. 6.93×10-4 mol min-1
2. 2.66 L min–1 at STP
3. 1.34×10-2 mol min-1
4. 6.93×10-2 mol min-1

Ans. 6.93×10-4 mol min-1

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Q9. A uniform string of length 20m is suspended from a rigid support. A short wave pulse is introduced at its lowest end. It starts moving up the string. The time taken to reach the support is: (take g = 10 ms–2)

1. 2 s
2. 2√2 s
3. √2s
4. 2π√2 s

Ans. 2√2 s

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Candidates can practice the JEE Main previous year's question papers and sample papers with solutions to easily crack the most difficult questions in JEE Main. Solving mock assessments will help the candidates identify the areas of challenges and to perform well in the exams