JEE Chemistry Practice Questions

Real exam: 90 questions · 180 minutes · +4 / −1 marking

22 free Chemistry MCQs written in the JEE exam pattern, each with a step-by-step solution. Tap an option for instant feedback — no sign-up, no ads.

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✍️ These are original practice questions written in the JEE pattern for the JEE Main engineering entrance exam — not questions from any official past paper.

Practice questions with solutions

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Periodic Table

Q1. The atomic number of carbon is:

  1. 12
  2. 6
  3. 8
  4. 14
Show answer

B. 6 — Carbon has 6 protons, so its atomic number is 6. Its most common isotope has mass number 12 (6 protons + 6 neutrons), which is a different quantity.

Physical Chemistry

Q2. The pH of a neutral aqueous solution at 25 °C is:

  1. 0
  2. 14
  3. 7
  4. 1
Show answer

C. 7 — At 25 °C a neutral solution has pH 7, where [H⁺] = [OH⁻] = 10⁻⁷ M. Below 7 is acidic, above 7 is basic.

Inorganic Chemistry

Q3. The most abundant gas in the Earth's atmosphere is:

  1. Oxygen
  2. Carbon dioxide
  3. Nitrogen
  4. Hydrogen
Show answer

C. Nitrogen — Nitrogen makes up about 78% of the atmosphere by volume, with oxygen about 21%. Carbon dioxide is only about 0.04%.

Chemical Bonding

Q4. A chemical bond formed by the sharing of electron pairs between atoms is called a:

  1. Ionic bond
  2. Covalent bond
  3. Metallic bond
  4. Hydrogen bond
Show answer

B. Covalent bond — A covalent bond forms when atoms share electron pairs. An ionic bond involves transfer of electrons; a metallic bond is a 'sea' of delocalised electrons; a hydrogen bond is a weak intermolecular attraction.

Periodic Table

Q5. The lightest element in the periodic table is:

  1. Helium
  2. Hydrogen
  3. Lithium
  4. Carbon
Show answer

B. Hydrogen — Hydrogen (atomic number 1) is the lightest element. Helium is second; lithium and carbon are heavier still.

Organic Chemistry

Q6. The functional group –OH is characteristic of:

  1. Aldehydes
  2. Carboxylic acids
  3. Alcohols
  4. Ketones
Show answer

C. Alcohols — The hydroxyl group –OH characterises alcohols. Aldehydes have –CHO, ketones have C=O within the chain, and carboxylic acids have –COOH.

Mole concept (Physical)

Q7. How many moles are present in 11 g of carbon dioxide (molar mass = 44 g/mol)?

  1. 0.25 mol
  2. 0.5 mol
  3. 0.75 mol
  4. 1.0 mol
Show answer

A. 0.25 mol — Moles = mass / molar mass = 11 / 44 = 0.25 mol.

Organic functional groups

Q8. The functional group -CHO is characteristic of which class of organic compounds?

  1. Alcohols
  2. Ketones
  3. Aldehydes
  4. Ethers
Show answer

C. Aldehydes — The formyl group -CHO defines the aldehyde class.

Electronic configuration (Inorganic)

Q9. An element has the ground-state electronic configuration 1s2 2s2 2p6 3s1. The element is:

  1. Sodium (Na)
  2. Magnesium (Mg)
  3. Potassium (K)
  4. Lithium (Li)
Show answer

A. Sodium (Na) — The configuration accounts for 11 electrons, so the element is sodium (Z = 11).

Gas laws (Physical)

Q10. At constant temperature, if the pressure on a fixed mass of an ideal gas is doubled, its volume becomes:

  1. Double the original
  2. Half the original
  3. Unchanged
  4. Four times the original
Show answer

B. Half the original — By Boyle's law V is proportional to 1/P, so doubling P halves the volume.

Oxidation states (Inorganic)

Q11. The oxidation state of manganese in potassium permanganate (KMnO4) is:

  1. +2
  2. +4
  3. +6
  4. +7
Show answer

D. +7 — (+1) + Mn + 4(-2) = 0 gives Mn = +7.

Hybridization (Organic)

Q12. The hybridization of each carbon atom in ethyne (C2H2) is:

  1. sp3
  2. sp2
  3. sp
  4. sp3d
Show answer

C. sp — Each carbon forms a triple bond and is therefore sp hybridized.

Thermodynamics (Physical)

Q13. For the isothermal expansion of an ideal gas, the change in internal energy (ΔU) is:

  1. Always positive
  2. Always negative
  3. Cannot be determined
  4. Zero
Show answer

D. Zero — Internal energy of an ideal gas depends only on temperature; ΔT = 0 makes ΔU = 0.

Chemical bonding (Inorganic)

Q14. The bonding in solid sodium chloride (NaCl) is predominantly:

  1. Covalent
  2. Ionic
  3. Metallic
  4. Hydrogen bonding
Show answer

B. Ionic — Electron transfer from Na to Cl gives an ionic lattice.

Atomic structure (Physical)

Q15. The maximum number of electrons that can be accommodated in the shell with principal quantum number n = 3 is:

  1. 2
  2. 8
  3. 32
  4. 18
Show answer

D. 18 — Maximum electrons = 2n^2 = 2(3)^2 = 18.

Aromatic hydrocarbons (Organic)

Q16. The molecular formula of benzene is:

  1. C6H6
  2. C6H12
  3. C6H14
  4. C5H10
Show answer

A. C6H6 — Benzene is the six-carbon aromatic ring C6H6.

Solutions and concentration (Physical)

Q17. A 1 molar (1 M) aqueous solution contains 1 mole of solute dissolved in:

  1. 1 litre of solvent
  2. 1 kilogram of solvent
  3. 1 litre of solution
  4. 1 mole of solvent
Show answer

C. 1 litre of solution — Molarity is moles of solute per litre of solution, not solvent.

Periodic trends (Inorganic)

Q18. On moving from left to right across a period in the periodic table, the atomic radius generally:

  1. Increases
  2. Decreases
  3. Remains constant
  4. Doubles
Show answer

B. Decreases — Increasing nuclear charge across a period pulls electrons inward, so radius decreases.

Ionic equilibrium / pH (Physical)

Q19. At 25°C, an aqueous solution has [H+] = 1×10^-3 M. Its pH is:

  1. 3
  2. 11
  3. 7
  4. 6
Show answer

A. 3 — pH = -log[H+] = -log(10^-3) = 3.

Organic reactions

Q20. Catalytic hydrogenation of an alkene (addition of H2) produces the corresponding:

  1. Alkyne
  2. Alcohol
  3. Alkyl halide
  4. Alkane
Show answer

D. Alkane — Adding H2 across the C=C double bond saturates it to an alkane.

S Block elements (Inorganic)

Q21. Which of the following elements is an alkaline earth metal?

  1. Sodium (Na)
  2. Calcium (Ca)
  3. Aluminium (Al)
  4. Iron (Fe)
Show answer

B. Calcium (Ca) — Alkaline earth metals are Group 2 elements; calcium belongs to Group 2.

Chemical kinetics (Physical)

Q22. The SI unit of the rate constant for a first-order reaction is:

  1. mol L^-1 s^-1
  2. L mol^-1 s^-1
  3. mol^-1 s
  4. s^-1
Show answer

D. s^-1 — For first order, rate = k[A], so k carries units of time^-1, i.e. s^-1.

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