Mole Conversion Worksheet with Answers (Grade 11 Chemistry)

This free mole conversion worksheet gives Grade 11 students 26 practice problems on the mole: molar mass, grams to moles, moles to grams, and moles to atoms or molecules.

It finishes with two-step conversions, two common errors to fix, and a challenge on counting atoms inside molecules. The answer key shows the full setup for every calculation, and every answer has been computed and checked to 3 significant figures.

• Grade 11 Chemistry
• 26 marks
• 40–50 minutes
• Worked answer key

What's in This Mole Conversion Worksheet

The problems build one step at a time, so students master each conversion before combining them.

Part	Skill practised	Marks
A	Calculate molar mass (including brackets)	6
B	Mass → moles	4
C	Moles → mass	4
D	Moles ↔ particles (Avogadro's number)	4
E	Two-step conversions: grams ↔ particles	4
F	Spot the mistake	2
G	Challenge: atoms inside molecules, and comparing samples	2

It supports the Ontario Grade 11 chemistry curriculum expectations in the Quantities in Chemical Reactions unit, and it is the foundation for stoichiometry.

The Mole Road Map

Every problem on this mole conversion worksheet is a trip along one road. Moles are always in the middle, so you can never jump straight from grams to particles.

• Mass → moles: n = m ÷ M, where M is the molar mass in g/mol.
• Moles → particles: N = n × N_A, where N_A = 6.02 × 10²³ (Avogadro's number).
• Molar mass is the sum of the atomic masses in the formula. Use the values printed on the worksheet, which come from the periodic table rounded to two decimals.

Worked Examples

Grams to moles

How many moles are in 36.0 g of water? Molar mass of H₂O = 2(1.01) + 16.00 = 18.02 g/mol, so n = 36.0 ÷ 18.02 = 2.00 mol.

Grams to molecules (two steps)

How many molecules are in 22.0 g of CO₂? First, 22.0 ÷ 44.01 = 0.500 mol. Then 0.500 × 6.02 × 10²³ = 3.01 × 10²³ molecules. This is question 20 on the mole conversion worksheet.

Mole Conversion Practice Problems

These match the mole conversion worksheet PDF. Give answers to 3 significant figures and use N_A = 6.02 × 10²³.

Part A – Molar Mass

Calculate the molar mass of each compound.

1. H₂O
2. CO₂
3. NaCl
4. CaCO₃
5. H₂SO₄
6. Al₂(SO₄)₃

Part B – Mass → Moles

7. Convert 36.0 g of H₂O to moles.
8. Convert 11.0 g of CO₂ to moles.
9. Convert 5.85 g of NaCl to moles.
10. Convert 250. g of CaCO₃ to moles.

Part C – Moles → Mass

11. Find the mass of 3.00 mol of NaCl.
12. Find the mass of 0.500 mol of H₂SO₄.
13. Find the mass of 2.50 mol of O₂.
14. Find the mass of 0.0250 mol of CaCO₃.

Part D – Moles ↔ Particles

15. How many atoms are in 2.00 mol of iron (Fe)?
16. How many molecules are in 0.250 mol of CO₂?
17. How many moles are in 3.01 × 10²³ molecules of H₂O?
18. How many moles are in 9.03 × 10²³ atoms of copper (Cu)?

Part E – Two-Step Conversions

19. How many molecules are in 9.01 g of H₂O?
20. How many molecules are in 22.0 g of CO₂?
21. What is the mass of 1.505 × 10²³ atoms of iron?
22. How many hydrogen atoms are in 2.00 mol of H₂O?

Part F – Spot the Mistake

23. To find the mass of 2.00 mol of NaCl, a student calculates 2.00 ÷ 58.44 = 0.0342 g. Explain the error and correct it.
24. A student says 1 mol of H₂ has the same mass as 1 mol of O₂. Explain the error and correct it.

Part G – Challenge

25. How many oxygen atoms are in 10.0 g of CO₂?
26. Which contains more molecules: 10.0 g of H₂O or 10.0 g of CO₂? Explain.

Mole Conversion Worksheet Answer Key

Each answer shows the setup, so students can find exactly where they went wrong. The printable key is on pages 3–4 of the PDF.

Part A answers (Q1–6)

1. H₂O: 18.02 g/mol
2. CO₂: 44.01 g/mol
3. NaCl: 58.44 g/mol
4. CaCO₃: 100.09 g/mol
5. H₂SO₄: 98.09 g/mol
6. Al₂(SO₄)₃: 342.17 g/mol

Part B answers (Q7–10)

7. n = 36.0 g ÷ 18.02 g/mol = 2.00 mol
8. n = 11.0 g ÷ 44.01 g/mol = 0.250 mol
9. n = 5.85 g ÷ 58.44 g/mol = 0.100 mol
10. n = 250. g ÷ 100.09 g/mol = 2.50 mol

Part C answers (Q11–14)

11. m = 3.00 mol × 58.44 g/mol = 175 g
12. m = 0.500 mol × 98.09 g/mol = 49.0 g
13. m = 2.50 mol × 32.00 g/mol = 80.0 g
14. m = 0.0250 mol × 100.09 g/mol = 2.50 g

Part D answers (Q15–18)

15. N = 2.00 × 6.02 × 10²³ = 1.20 × 10²⁴ atoms
16. N = 0.250 × 6.02 × 10²³ = 1.51 × 10²³ molecules
17. n = 3.01 × 10²³ ÷ 6.02 × 10²³ = 0.500 mol
18. n = 9.03 × 10²³ ÷ 6.02 × 10²³ = 1.50 mol

Part E answers (Q19–22)

19. 9.01 ÷ 18.02 = 0.500 mol; × 6.02 × 10²³ = 3.01 × 10²³ molecules
20. 22.0 ÷ 44.01 = 0.500 mol; × 6.02 × 10²³ = 3.01 × 10²³ molecules
21. 1.505 × 10²³ ÷ 6.02 × 10²³ = 0.250 mol; × 55.85 = 14.0 g
22. 2.00 mol × 2 H per molecule × 6.02 × 10²³ = 2.41 × 10²⁴ H atoms

Part F answers (Q23–24)

23. Mass = moles × molar mass, not moles ÷ molar mass. Correct: 2.00 × 58.44 = 117 g
24. They have the same number of molecules, but different molar masses: 2.02 g vs 32.00 g.

Part G answers (Q25–26)

25. 10.0 ÷ 44.01 = 0.227 mol CO₂; × 2 × 6.02 × 10²³ = 2.74 × 10²³ O atoms
26. H₂O: 0.555 mol vs 0.227 mol CO₂. Water has the smaller molar mass, so the same mass contains more moles and more molecules.

5 Common Mole Conversion Mistakes

Part F of the mole conversion worksheet targets the first two directly.

1. Dividing when you should multiply. Moles → grams means multiplying by molar mass. If your answer is tiny when you expected grams, check the operation.
2. Thinking a mole of anything has the same mass. One mole always has the same number of particles, but its mass depends on the molar mass.
3. Skipping the mole step. Grams cannot be converted straight to molecules. Always go through moles.
4. Miscounting brackets in molar mass. In Al₂(SO₄)₃, the 3 multiplies both S and O, giving 3 S and 12 O.
5. Mixing up molecules and atoms. One H₂O molecule contains 2 H atoms, so 2.00 mol of water holds 2.41 × 10²⁴ H atoms.

How to Use This Mole Conversion Worksheet in Class

As a teacher, I spread it over the start of the quantities unit:

• Day 1: Parts A–C after introducing molar mass.
• Day 2: Part D after Avogadro's number, then Part E as pair work.
• Review: Parts F and G as an exit ticket. Part G shows quickly who understands the difference between moles of molecules and moles of atoms.

Students can check molar masses with our free chemistry calculators, then move on to the stoichiometry quiz and the stoichiometry calculation quiz.

Frequently Asked Questions

Is this mole conversion worksheet free?

Yes. The worksheet and answer key are free to download and print as a PDF, with no account needed.

How do you convert grams to moles?

Divide the mass by the molar mass: n = m ÷ M. For example, 36.0 g of water ÷ 18.02 g/mol = 2.00 mol.

How do you convert moles to particles?

Multiply by Avogadro's number, 6.02 × 10^23. Two moles of iron contain 2.00 × 6.02 × 10^23 = 1.20 × 10^24 atoms.

How do you go from grams to number of molecules?

Always go through moles. Divide grams by molar mass to get moles, then multiply by 6.02 × 10^23 to get molecules.

What grade is this mole conversion worksheet for?

It is written for Grade 11 chemistry and is also a good refresher before Grade 12 stoichiometry and equilibrium.

More Free Grade 11 Chemistry Resources

• Balancing Chemical Equations WorksheetNeeded for stoichiometry
• Types of Chemical Reactions WorksheetPredict, then calculate
• Naming Ionic Compounds WorksheetWrite formulas correctly
• Scientific Notation QuizHandle 10²³ with ease
• All Grade 11 ResourcesWorksheets and quizzes

Ready to practise? Download the free mole conversion worksheet PDF (use the Download button above), print it double-sided, and keep the answer key pages for marking.