“Mole Concept” MCQ with Answer Explanation : NEET 2025.

21. How many moles are in 12 g of C (Molar mass = 12 g/mol)?
    a) 1 mole
    b) 2 moles
    c) 0.5 moles
    d) 3 moles

Answer: a) 1 mole

Explanation: 12 g ÷ 12 g/mol = 1 mole.

22. Which of the following describes a chemical change?
    a) Dissolving salt in water
    b) Melting ice
    c) Rusting of iron
    d) Boiling water

Answer: c) Rusting of iron

Explanation: Rusting involves a chemical transformation, while the others are physical changes.

23. In the reaction 3H₂ + N₂ → 2NH₃, what is the mole ratio of H₂ to NH₃?
    a) 1:2
    b) 2:3
    c) 3:2
    d) 1:1

Answer: c) 3:2

Explanation: The coefficients indicate that 3 moles of hydrogen produce 2 moles of ammonia.

24. What is the molar mass of sodium sulfate (Na₂SO₄)?
    a) 122 g/mol
    b) 142 g/mol
    c) 138 g/mol
    d) 98 g/mol

Answer: b) 142 g/mol

Explanation: Molar mass is calculated as (2 × 23) + 32 + (4 × 16) = 142 g/mol.

25. If you have 4.5 moles of a substance, how many molecules do you have?
    a) 2.71 × 10²³
    b) 2.71 × 10²⁴
    c) 4.5 × 6.022 × 10²³
    d) 3.01 × 10²⁴

Answer: b) 2.71 × 10²⁴

Explanation: 4.5 moles × 6.022 × 10²³ molecules/mole = 2.71 × 10²⁴ molecules.

26. What is the number of grams in 2.5 moles of C₆H₁₂O₆ (Molar mass = 180 g/mol)?
    a) 450 g
    b) 360 g
    c) 270 g
    d) 540 g

Answer: a) 450 g

Explanation: 2.5 moles × 180 g/mol = 450 g.

27. Which of the following gases will have the largest volume at STP when 1 mole is considered?
    a) N₂
    b) O₂
    c) CO₂
    d) All will have the same volume

Answer: d) All will have the same volume

Explanation: At STP, 1 mole of any ideal gas occupies the same volume (22.4 L).

28. How many moles are in 88 g of CH₄ (Molar mass = 16 g/mol)?
    a) 2 moles
    b) 5.5 moles
    c) 6 moles
    d) 4 moles

Answer: a) 5.5 moles

Explanation: 88 g ÷ 16 g/mol = 5.5 moles.

29. In the reaction: 2H₂ + O₂ → 2H₂O, how many moles of H₂ are needed to produce 3 moles of H₂O?
    a) 2.5 moles
    b) 3 moles
    c) 4.5 moles
    d) 3.5 moles

Answer: a) 2.5 moles

Explanation: The mole ratio shows that for every 2 moles of H₂O produced, 2 moles of H₂ are needed, so 3 moles of H₂O require 2.5 moles of H₂.

30. What is the molar mass of ammonium sulfate ((NH₄)₂SO₄)?
    a) 132 g/mol
    b) 132.14 g/mol
    c) 145 g/mol
    d) 150 g/mol

Answer: a) 132 g/mol

Explanation: Molar mass is calculated as (2 × 14) + (8 × 1) + 32 + (4 × 16) = 132 g/mol.