Some Basic Concepts In Chemistry JEE Mains Questions - List Of Most Asked Questions With Solutions

NTA will shortly release the JEE Main Syllabus 2025 at jeemain.nta.ac.in. Last Year, the complete syllabus of JEE Main underwent some major changes. According to the latest syllabus guidelines, the weightage of Physics has dropped to 22.5%. Due to these changes in the syllabus, certain shifts in chapter-wise weightage have been observed. Some basic parts of Chemistry are among such topics. It’s among the least weightage topics in JEE Main ChemistrySyllabus 2025. This chapter holds 1.39% weightage in the whole syllabus.

• Some basic parts of Chemistry are a part of the General Chemistry Section, and every year around 2-3 questions are asked from this chapter. Due to the drop in weightage, you can expect 1-2 questions in JEE Main 2025.
• Some basic parts of Chemistry in JEE Mains Chemistry Syllabus 2025 covers all the basic concepts on units and measurements, fundamentals of units, dimensions etc.

Aspirants consider Some basic parts of Chemistry as one of the Easiest Chapters in Chemistry for JEE Main 2025. Even though this chapter has the least weightage in the syllabus, to develop a strong foundation in physics, this particular chapter plays a pivotal role. Hence the candidates need to develop a clear understanding of this chapter. The list of most asked questions from this chapter will help the students with their preparation.

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Some Basic Parts of Chemistry JEE Mains Questions -

List Of Most Asked Questions With Solutions

In the (JEE) Main, the topic of Physics and Measurement often features questions that have appeared multiple times in previous years. Many questions in this section are either repeated or follow similar patterns, with only minor changes, such as different numerical values or slight modifications in wording.Certain questions have been repeated as many as five times.

Here are some of the most frequently asked and repeated questions:

Question:

What is the empirical formula of a compound that contains 40% carbon, 6.67% hydrogen, and 53.33% oxygen by mass?

Solution:

Correct answer: CH₂O. Explanation: Divide the mass percentages by atomic masses to find the simplest ratio.

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)

Question:

Which of the following is the correct molarity of a solution containing 5 grams of NaOH in 500 mL of solution?

Solution:

Correct answer: 0.25 M. Explanation: Molarity = moles of solute / volume of solution (L).

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)

Question:

How many moles of oxygen are required to completely burn 2 moles of propane (C₃H₈)?

Solution:

Correct answer: 10 moles. Explanation: The balanced equation is C₃H₈ + 5O₂ → 3CO₂ + 4H₂O.

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)

Question:

What is the mass of one mole of carbon dioxide (CO₂)?

Solution:

Correct answer: 44 g/mol. Explanation: Add the atomic masses of carbon (12) and oxygen (16×2).

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)

Question:

Which of the following contains the greatest number of moles: 16 g of methane (CH₄), 44 g of CO₂, or 18 g of H₂O?

Solution:

Correct answer: 16 g of CH₄. Explanation: Calculate moles for each by dividing mass by molar mass.

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)

Question:

If 0.5 mole of N₂ reacts with 1.5 moles of H₂ according to the equation N₂ + 3H₂ → 2NH₃, how many moles of NH₃ will be formed?

Solution:

Correct answer: 0.5 moles. Explanation: Use stoichiometric ratios from the balanced equation.

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)

Question:

What is the molar mass of sulfuric acid (H₂SO₄)?

Solution:

Correct answer: 98 g/mol. Explanation: Add the atomic masses of hydrogen (2×1), sulfur (32), and oxygen (4×16).

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)

Question: How many molecules are present in 22.4 liters of nitrogen gas at STP?

Solution: Correct answer: 6.022 × 10²³ molecules. Explanation: One mole of gas at STP occupies 22.4 liters.

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)

Question:

What is the mass of 0.5 moles of water (H₂O)?

Solution:

Correct answer: 9 grams. Explanation: Molar mass of H₂O is 18 g/mol, so 0.5 moles is 9 grams.

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)

Question:

How many grams of NaOH are required to prepare 250 mL of a 0.1 M NaOH solution?

Solution:

Correct answer: 1 gram. Explanation: Moles = Molarity × Volume; mass = moles × molar mass.

(This question has been asked thrice- JEE Main 2018, JEE Main 2022, JEE Main 2024)