Question 1Warm-upFoundation
20 g of salt is dissolved to make 2 dm³ of solution. Calculate the concentration in g/dm³.
Mass ÷ volume.
Worked solution
- g/dm³
Answer: g/dm³
GCSE & IGCSE chemistry practice
Concentration questions and answers
Concentration is how much solute is dissolved in a volume of solution. In g/dm³: concentration = mass ÷ volume. In mol/dm³: concentration = moles ÷ volume. Volume must be in dm³: 1 dm³ = 1000 cm³. Relative atomic masses: H = 1, C = 12, N = 14, O = 16, Na = 23, Mg = 24, Al = 27, S = 32, Cl = 35.5, K = 39, Ca = 40, Fe = 56, Cu = 63.5.
8 questions · Foundation and Higher tier · Every answer is checked as you type it, with a full worked solution. Updated .
Where concentration comes up
| GCSE (AQA) | Chemistry and Combined Science, Foundation and Higher: concentration in g/dm³. GCSE Chemistry only, Higher only: concentration in mol/dm³. |
|---|---|
| Cambridge IGCSE (0620) | Core: know concentration can be measured in g/dm³ or mol/dm³. Supplement: calculate concentrations and volumes of solutions, including converting cm³ to dm³. |
The method
- Convert cm³ to dm³: divide by 1000.
- g/dm³ = mass (g) ÷ volume (dm³).
- mol/dm³ = moles ÷ volume (dm³).
- Mass = concentration × volume. g/dm³ ÷ Mr = mol/dm³.
Concentration questions
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Warm-up
Question 2Warm-upFoundation
5 g of sugar is dissolved to make 250 cm³ of solution. Calculate the concentration in g/dm³.
250 cm³ = 0.25 dm³.
Worked solution
- g/dm³
Answer: g/dm³
Exam-style
Question 3Exam-styleFoundation
What mass of solute is in 500 cm³ of a 40 g/dm³ solution?
Mass = concentration × volume (in dm³).
Worked solution
- g
Answer: g
Question 4Exam-styleHigher
0.5 mol of sodium hydroxide is dissolved to make 250 cm³ of solution. Calculate the concentration in mol/dm³.
Moles ÷ volume in dm³.
Worked solution
- mol/dm³
Answer: mol/dm³
Question 5Exam-styleHigher
How many moles of hydrochloric acid are in 25 cm³ of a 0.1 mol/dm³ solution?
Moles = concentration × volume (dm³).
Worked solution
- mol
Answer: mol
Question 6Exam-styleHigher
4 g of sodium hydroxide (NaOH) is dissolved to make 500 cm³ of solution. Calculate the concentration in mol/dm³. (Na = 23, O = 16, H = 1)
Mr of NaOH = 40.
Worked solution
- Moles
- mol/dm³
Answer: mol/dm³
Challenge
Question 7ChallengeHigher
A sulfuric acid solution is 0.5 mol/dm³. What is its concentration in g/dm³? ( of = 98)
g/dm³ = mol/dm³ × Mr.
Worked solution
- g/dm³
Answer: g/dm³
Question 8ChallengeHigher
What mass of sodium chloride is needed to make 200 cm³ of a 1.5 mol/dm³ solution? (Na = 23, Cl = 35.5)
Moles = 1.5 × 0.2.
Worked solution
- Moles
- Mass g
Answer: g
Common mistakes
- Dividing by a volume in cm³.
- Dividing cm³ by 100 instead of 1000.
- Mixing up g/dm³ and mol/dm³.
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Sources
The questions are our own. The “where it comes up” notes are from each board's published specification, checked on 27 October 2026:
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