Questions on Conversions Between Moles and Mass

Conversions between moles and mass are among the most important quantitative skills in chemistry because they connect measurable amounts of matter with the mole concept and chemical equations. Developed by a Science Teacher and Education Specialist, this collection of questions combines scientific rigor with practical classroom experience. The material is intended to help teachers, homeschool educators, and students master stoichiometric calculations and prepare effectively for chemistry examinations.

Conversions between moles and mass are based on the molar mass of a substance, which serves as the bridge between the amount of substance and its measurable mass. By using molar mass as a conversion factor, chemists can determine the number of moles in a given mass or calculate the mass corresponding to a specific number of moles. This concept is fundamental to stoichiometry, chemical reactions, and quantitative analysis.

Multiple-Choice Questions: Conversions Between Moles and Mass

1. What is the mass of 1 mole of water (H₂O)?

A) 10.0 g

B) 16.0 g

C) 18.0 g

D) 20.0 g

E) 2.0 g

2. How many grams are in 2 moles of sodium (Na)? (Na = 23.0 g/mol)

A) 11.5 g

B) 46.0 g

C) 23.0 g

D) 92.0 g

E) 69.0 g

3. How many moles are in 36.0 g of water (H₂O)? (H₂O = 18.0 g/mol)

A) 1 mol

B) 2 mol

C) 3 mol

D) 4 mol

E) 0.5 mol

4. What is the molar mass of carbon dioxide (CO₂)?

A) 28.0 g/mol

B) 44.0 g/mol

C) 32.0 g/mol

D) 40.0 g/mol

E) 12.0 g/mol

5. How many moles are in 88.0 g of CO₂? (CO₂ = 44.0 g/mol)

A) 1 mol

B) 2 mol

C) 3 mol

D) 4 mol

E) 0.5 mol

6. Find the mass of 0.5 mol of nitrogen gas (N₂). (N₂ = 28.0 g/mol)

A) 14.0 g

B) 28.0 g

C) 56.0 g

D) 7.0 g

E) 21.0 g

7. What is the molar mass of NaCl? (Na = 23.0, Cl = 35.5)

A) 58.5 g/mol

B) 46.5 g/mol

C) 35.5 g/mol

D) 23.0 g/mol

E) 80.0 g/mol

8. How many grams are in 3 mol of NaCl?

A) 58.5 g

B) 117.0 g

C) 175.5 g

D) 29.25 g

E) 3.0 g

9. How many moles are in 98.0 g of H₂SO₄? (H = 1.0, S = 32.0, O = 16.0)

A) 1 mol

B) 2 mol

C) 3 mol

D) 0.5 mol

E) 4 mol

10. How many grams are in 4 mol of methane (CH₄)? (C = 12.0, H = 1.0)

A) 16.0 g

B) 64.0 g

C) 44.0 g

D) 32.0 g

E) 28.0 g

11. The molar mass of glucose (C₆H₁₂O₆) is approximately:

A) 180.0 g/mol

B) 160.0 g/mol

C) 120.0 g/mol

D) 150.0 g/mol

E) 100.0 g/mol

12. How many moles are in 90.0 g of glucose (C₆H₁₂O₆)?

A) 0.25 mol

B) 0.5 mol

C) 1 mol

D) 2 mol

E) 3 mol

13. What is the mass of 1.5 mol of O₂? (O₂ = 32.0 g/mol)

A) 48.0 g

B) 32.0 g

C) 64.0 g

D) 16.0 g

E) 96.0 g

14. Which of the following masses contains 1 mole of substance?

A) 24.0 g of Mg

B) 2.0 g of H₂

C) 18.0 g of H₂O

D) All of the above

E) Only A and C

15. How many grams are in 0.25 mol of calcium chloride (CaCl₂)? (Ca = 40.0, Cl = 35.5)

A) 27.9 g

B) 50.0 g

C) 55.5 g

D) 22.2 g

E) 27.75 g

16. How many moles are in 16.0 g of CH₄?

A) 2 mol

B) 1 mol

C) 0.5 mol

D) 4 mol

E) 8 mol

17. What is the mass of 2.5 mol of sulfur (S)? (S = 32.0 g/mol)

A) 64.0 g

B) 80.0 g

C) 96.0 g

D) 100.0 g

E) 120.0 g

18. Which has a mass closest to 1 mole?

A) 44.0 g of CO₂

B) 2.0 g of H₂

C) 58.5 g of NaCl

D) All of the above

E) Only A and C

19. How many grams are in 0.1 mol of ammonia (NH₃)? (N = 14.0, H = 1.0)

A) 1.7 g

B) 10.0 g

C) 17.0 g

D) 0.17 g

E) 1.0 g

20. How many moles are in 4.00 g of helium (He = 4.00 g/mol)?

A) 2 mol

B) 1 mol

C) 0.5 mol

D) 4 mol

E) 0.25 mol

Answers with Explanations

1. C) 18.0 g — H₂O = (2×1.0) + 16.0 = 18.0 g/mol

2. B) 46.0 g — 2 mol × 23.0 g/mol

3. B) 2 mol — 36.0 ÷ 18.0

4. B) 44.0 g/mol — C = 12.0, O₂ = 2×16.0

5. B) 2 mol — 88.0 ÷ 44.0

6. A) 14.0 g — 0.5 mol × 28.0

7. A) 58.5 g/mol — 23.0 + 35.5

8. C) 175.5 g — 3 × 58.5

9. A) 1 mol — H₂SO₄ = 2×1.0 + 32.0 + 4×16.0 = 98.0

10. B) 64.0 g — CH₄ = 16.0 × 4 mol

11. A) 180.0 g/mol — (6×12.0) + (12×1.0) + (6×16.0)

12. B) 0.5 mol — 90.0 ÷ 180.0

13. A) 48.0 g — 1.5 mol × 32.0

14. D) All of the above — All represent 1 mol by mass

15. E) 27.75 g — CaCl₂ = 40.0 + 2×35.5 = 111.0 → 0.25 mol × 111.0

16. B) 1 mol — CH₄ = 16.0 g/mol

17. B) 80.0 g — 2.5 × 32.0

18. D) All of the above — Each value is the molar mass of the compound

19. A) 1.7 g — NH₃ = 17.0 g/mol × 0.1

20. B) 1 mol — 4.00 ÷ 4.00 = 1 mol

Questions on Conversions Between Moles and Mass

Practical Classroom Applications

Teachers can use this topic in several ways:

• Mole and mass conversion worksheets for guided and independent practice.

• Stoichiometry review activities connecting chemical formulas and quantities.

• Dimensional analysis exercises to reinforce unit conversions.

• Group problem-solving sessions that strengthen quantitative reasoning.

• Preparation for chemistry exams and standardized tests.

• Laboratory calculations involving reactants, products, and chemical equations.

• Real-world examples from pharmaceuticals, environmental science, and industrial chemistry.

• Interactive classroom activities using periodic tables and molecular models.

Explaining how mole and mass conversions are applied in chemical manufacturing, medicine, agriculture, environmental monitoring, and scientific research. Demonstrating these applications helps students appreciate the importance of quantitative chemistry in both everyday life and professional scientific fields.

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Ronaldo Silva: Professor and Specialist in Science Education from University Federal FLuminense/RJ, with over 25 years of teaching experience..

Questions on Conversions Between Moles and Mass