Molarity Worksheet with Answers (Grade 11 Chemistry)

This free molarity worksheet gives Grade 11 students 22 problems on solution concentration: finding molarity, preparing solutions, diluting stock solutions and working out ion concentrations.

The student copy has ruled space to show every step, and the answer key shows the full working. Every answer has been calculated and checked to 3 significant figures.

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

What's in This Molarity Worksheet

The problems build from the basic formula to multi-step and mixing problems.

Part	Skill practised	Marks
A	Molarity from moles and volume	4
B	Molarity from mass	6
C	Preparing a solution: mass of solute needed	6
D	Moles and volume from molarity	2
E	Dilution with c₁V₁ = c₂V₂	4
F	Ion concentrations	2
G	Spot the mistake	2
H	Challenge: mixing solutions and neutralization	2

It supports the Ontario Grade 11 chemistry curriculum expectations in the Solutions and Solubility unit.

The Molarity Formula

Molarity (c) is moles of solute per litre of solution. Every problem on this molarity worksheet uses this formula or a rearrangement of it. The two most important habits are to convert millilitres to litres and, when you're given grams, to convert to moles first. For a refresher on grams and moles, see the mole conversion worksheet.

Example: 11.7 g of NaCl dissolved to make 200. mL of solution. n = 11.7 ÷ 58.44 = 0.200 mol, and V = 0.200 L, so c = 0.200 ÷ 0.200 = 1.00 mol/L.

Dilution: c₁V₁ = c₂V₂

Adding water spreads the same moles of solute through more volume, so concentration drops while c × V stays constant.

Example: 50.0 mL of 6.00 mol/L HCl is diluted to 300. mL. c₂ = (6.00 × 50.0) ÷ 300. = 1.00 mol/L. Any volume unit works here, as long as both sides use the same one. For more background, see molar concentration on Wikipedia.

Molarity Practice Problems

These match the molarity worksheet PDF. Give answers to 3 significant figures.

Part A – Molarity From Moles and Volume

1. 2.00 mol of NaCl is dissolved to make 1.00 L of solution. Find the molarity.
2. 0.500 mol of KCl is dissolved to make 250. mL of solution. Find the molarity.
3. 0.150 mol of HCl is dissolved to make 500. mL of solution. Find the molarity.
4. 0.0250 mol of NaOH is dissolved to make 100. mL of solution. Find the molarity.

Part B – Molarity From Mass

5. 11.7 g of NaCl is dissolved to make 200. mL of solution. Find the molarity.
6. 4.00 g of NaOH is dissolved to make 250. mL of solution. Find the molarity.
7. 90.1 g of C₆H₁₂O₆ is dissolved to make 1.00 L of solution. Find the molarity.

Part C – Preparing a Solution: Mass Needed

8. What mass of NaCl is needed to make 500. mL of a 0.200 mol/L solution?
9. What mass of KNO₃ is needed to make 250. mL of a 0.400 mol/L solution?
10. What mass of CuSO₄ is needed to make 100. mL of a 0.150 mol/L solution?

Part D – Moles and Volume From Molarity

11. How many moles of HCl are in 75.0 mL of a 0.200 mol/L solution?
12. What volume of 0.250 mol/L NaOH contains 0.0500 mol of NaOH?

Part E – Dilution

13. 50.0 mL of 6.00 mol/L HCl is diluted to 300. mL. What is the new concentration?
14. What volume of 12.0 mol/L HCl is needed to make 500. mL of 0.600 mol/L HCl?
15. How much water must be added to 100. mL of 2.00 mol/L NaCl to make it 0.500 mol/L?
16. 25.0 mL of 0.800 mol/L KCl is diluted to 200. mL. What is the new concentration?

Part F – Ion Concentrations

17. What is [Cl⁻] in 0.150 mol/L CaCl₂?
18. What are [Na⁺] and [SO₄²⁻] in 0.200 mol/L Na₂SO₄?

Part G – Spot the Mistake

19. A student finds the molarity of 0.500 mol of NaCl in 250. mL as 0.500 ÷ 250 = 0.00200 mol/L. Explain the error and correct it.
20. To make 500. mL of 1.00 mol/L NaCl, a student adds 29.2 g of NaCl to 500. mL of water. Explain the error and correct it.

Part H – Challenge

21. 100. mL of 0.200 mol/L NaCl is mixed with 50.0 mL of 0.500 mol/L NaCl. What is the final concentration?
22. HCl + NaOH → NaCl + H₂O. What volume of 0.100 mol/L HCl neutralizes 25.0 mL of 0.200 mol/L NaOH?

Molarity Worksheet Answer Key

Each answer shows the full working. The printable key is at the end of the PDF.

Part A answers (Q1–4)

1. c = 2.00 mol ÷ 1.00 L = 2.00 mol/L
2. c = 0.500 mol ÷ 0.250 L = 2.00 mol/L
3. c = 0.150 mol ÷ 0.500 L = 0.300 mol/L
4. c = 0.0250 mol ÷ 0.100 L = 0.250 mol/L

Part B answers (Q5–7)

5. n = 11.7 ÷ 58.44 = 0.200 mol; c = 0.200 ÷ 0.200 L = 1.00 mol/L
6. n = 4.00 ÷ 40.00 = 0.100 mol; c = 0.100 ÷ 0.250 L = 0.400 mol/L
7. n = 90.1 ÷ 180.18 = 0.500 mol; c = 0.500 ÷ 1.00 L = 0.500 mol/L

Part C answers (Q8–10)

8. n = 0.200 × 0.500 L = 0.100 mol; m = 0.100 × 58.44 = 5.84 g
9. n = 0.400 × 0.250 L = 0.100 mol; m = 0.100 × 101.11 = 10.1 g
10. n = 0.150 × 0.100 L = 0.0150 mol; m = 0.0150 × 159.62 = 2.39 g

Part D answers (Q11–12)

11. n = 0.200 × 0.0750 L = 0.0150 mol
12. V = 0.0500 ÷ 0.250 = 0.200 L (200 mL)

Part E answers (Q13–16)

13. c₂ = (6.00 × 50.0) ÷ 300. = 1.00 mol/L
14. V₁ = (0.600 × 500.) ÷ 12.0 = 25.0 mL
15. V₂ = (2.00 × 100.) ÷ 0.500 = 400. mL; water added = 400. − 100. = 300 mL
16. c₂ = (0.800 × 25.0) ÷ 200. = 0.100 mol/L

Part F answers (Q17–18)

17. CaCl₂ → Ca²⁺ + 2Cl⁻, so [Cl⁻] = 2 × 0.150 = 0.300 mol/L
18. Na₂SO₄ → 2Na⁺ + SO₄²⁻: [Na⁺] = 0.400 mol/L, [SO₄²⁻] = 0.200 mol/L

Part G answers (Q19–20)

19. Volume must be in litres: 250. mL = 0.250 L. Correct: 0.500 ÷ 0.250 = 2.00 mol/L
20. Molarity uses the volume of the solution, not the water. Dissolve the NaCl in some water, then add water up to the 500. mL mark in a volumetric flask.

Part H answers (Q21–22)

21. n = 0.200 × 0.100 + 0.500 × 0.0500 = 0.0450 mol; V = 0.150 L; c = 0.300 mol/L
22. n(NaOH) = 0.200 × 0.0250 = 0.00500 mol = n(HCl) (1 : 1); V = 0.00500 ÷ 0.100 = 0.0500 L = 50.0 mL

5 Common Molarity Mistakes

Part G of the molarity worksheet targets the first two.

1. Leaving volume in mL. 0.500 mol in 250 mL is 2.00 mol/L, not 0.00200 mol/L.
2. Using the volume of water instead of the solution. Dissolve the solute, then fill to the mark.
3. Using grams in c = n ÷ V. Convert to moles first.
4. Forgetting the ion ratio. CaCl₂ gives two Cl⁻ ions, so [Cl⁻] is double the salt's concentration.
5. Reporting total volume instead of water added. Diluting 100. mL to 400. mL means adding 300. mL of water.

How to Use This Molarity Worksheet in Class

• Day 1: Parts A–C after introducing molarity, ideally before a solution-preparation lab.
• Day 2: Parts D–F with dilution.
• Review: Parts G and H. The neutralization question previews titration.

Then check understanding with the solutions and solubility quiz, or move on to the acids and bases quiz.

Frequently Asked Questions

Is this molarity worksheet free?

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

What is the formula for molarity?

Molarity (c) = moles of solute (n) ÷ volume of solution in litres (V). Its unit is mol/L, sometimes written M.

How do you calculate molarity from grams?

Convert grams to moles by dividing by molar mass, convert the volume to litres, then divide moles by litres.

How does the dilution formula work?

c1V1 = c2V2. Adding water doesn't change the moles of solute, so concentration × volume stays the same before and after. Any volume unit works as long as you use the same one on both sides.

What grade is this molarity worksheet for?

It is written for Grade 11 chemistry and is also a useful review before Grade 12 titration and equilibrium.

More Free Grade 11 Chemistry Resources

• Mole Conversion WorksheetGrams to moles first
• Limiting Reactant WorksheetStoichiometry practice
• Empirical Formula WorksheetPercent composition
• Free Chemistry CalculatorsCheck your molar masses
• All Grade 11 ResourcesWorksheets and quizzes

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