9 Most Difficult Questions in JEE Main with Answers

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

In this article, we have highlighted the top 9 most difficult question in JEE Main based on previous year analysis along with solution. Practicing these questions effectively will help you crack any similar question type in the JEE Main exam 2026

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

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+

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

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

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

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

You 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 you identify the areas of challenges and to perform well in the exams

Conclusion

The most difficult questions in JEE Main test not only conceptual understanding but also analytical thinking, problem-solving speed, and accuracy across Physics, Chemistry, and Mathematics. As seen from the questions above, these problems often integrate multiple concepts, require clarity of fundamentals, and demand consistent practice. To tackle such challenging questions confidently, you must thoroughly understand the JEE Main syllabus and exam pattern, regularly solve previous years’ papers, and practice mock tests under exam-like conditions.

With focused preparation, strategic revision, and continuous self-assessment, even the toughest JEE Main questions can be approached systematically, significantly improving overall performance and boosting the chances of success in the examination.