🧪 Mole Concept — Practice Worksheet

Q1. The number of molecules in 1 mole of any substance is:

1. 6.022 × 10²²
2. 6.022 × 10²³
3. 6.022 × 10²⁴
4. 6.022 × 10²⁰

Q2. The molar mass of CaCO₃ is (Ca = 40, C = 12, O = 16):

1. 84 g/mol
2. 100 g/mol
3. 110 g/mol
4. 68 g/mol

Q3. The number of moles in 9 g of water (H₂O) is:

1. 0.25
2. 0.5
3. 1
4. 2

Q4. At STP, 1 mole of an ideal gas occupies:

1. 11.2 L
2. 22.4 L
3. 44.8 L
4. 2.24 L

Q5. The empirical formula of a compound containing 40% carbon, 6.7% hydrogen, and 53.3% oxygen is (C = 12, H = 1, O = 16):

1. CHO
2. CH₂O
3. C₂H₄O₂
4. CH₃O

Q6. The number of atoms in 0.5 moles of nitrogen gas (N₂) is:

1. 3.011 × 10²³
2. 6.022 × 10²³
3. 1.505 × 10²³
4. 12.044 × 10²³

Q7. The mass of 3.011 × 10²³ molecules of methane (CH₄) is:

1. 4 g
2. 8 g
3. 16 g
4. 32 g

Q8. In the reaction 2H₂ + O₂ → 2H₂O, the volume of oxygen at STP required to react with 4 moles of H₂ is:

1. 22.4 L
2. 44.8 L
3. 11.2 L
4. 89.6 L

Q9. The percentage of nitrogen in urea (NH₂CONH₂) is (N = 14, H = 1, C = 12, O = 16):

1. 23.3%
2. 46.7%
3. 32.3%
4. 14%

Q10. Which of the following has the maximum number of molecules?

1. 1 g of H₂
2. 1 g of O₂
3. 1 g of N₂
4. 1 g of CO₂

Q11. The equivalent weight of H₂SO₄ in the reaction H₂SO₄ → 2H⁺ + SO₄²⁻ is:

1. 98
2. 49
3. 32
4. 64

Q12. The molarity of a solution containing 4 g of NaOH in 500 mL of solution is (Na = 23, O = 16, H = 1):

1. 0.1 M
2. 0.2 M
3. 0.5 M
4. 1 M

Q13. Calculate the number of molecules in 11.2 L of CO₂ at STP.

Q14. A compound has the empirical formula CH₂O and a molar mass of 180 g/mol. Find its molecular formula.

Q15. How many grams of oxygen are required to completely burn 3 moles of methane? (CH₄ + 2O₂ → CO₂ + 2H₂O)

Q16. Calculate the molality of a solution prepared by dissolving 5.85 g of NaCl in 250 g of water (Na = 23, Cl = 35.5).

Q17. 5.6 g of an element reacts with oxygen to form 8.0 g of oxide. If the element has a valency of 2, find its atomic mass.

Q18. In the reaction Zn + 2HCl → ZnCl₂ + H₂, calculate the volume of H₂ at STP produced when 13 g of Zn reacts completely (Zn = 65).

Q19. A sample of hydrated copper sulphate (CuSO₄·xH₂O) weighing 25 g on heating gives 16 g of anhydrous salt. Find the value of x (Cu = 63.5, S = 32, O = 16, H = 1).

Q20. 100 mL of 0.5 M HCl is mixed with 100 mL of 0.3 M NaOH. Find the concentration of the resulting solution and identify whether it is acidic, basic, or neutral.