⚗️

IGCSE Chemistry Past Papers

Topic 3.3.3: Concentration Calculations

Questions

Total Marks

Paper 4

Style

⚠️Examination Instructions

•Answer ALL questions in the spaces provided
•Show ALL working - partial marks available
•Standard form: 1 dm³ = 1000 cm³
•Formula: n = C × V, C = n/V, V = n/C
•Click "Reveal Answer" to check your work after attempting each question

Section A: Units & Conversions

Foundation skills - essential for ALL concentration calculations

Question A1[1 mark]

Convert 500 cm³ into dm³.

Question A2[1 mark]

State the unit for molar concentration.

Question A3[1 mark]

Convert 2.5 dm³ into cm³.

Question A4[1 mark]

A solution has a volume of 250 cm³. Express this in dm³.

Question A5[1 mark]

State the alternative unit for mass concentration.

Section B: Molar Concentration Calculations

Core Paper 4 skills - using n = C × V

Question B1[2 marks]

Calculate the number of moles of HCl in 25 cm³ of a 2.0 mol/dm³ solution.

Question B2[3 marks]

A solution contains 0.1 mol of NaOH dissolved in 500 cm³ of water. Calculate the concentration in mol/dm³.

Question B3[2 marks]

Calculate the volume (in dm³) of a 1.5 mol/dm³ H₂SO₄ solution that contains 0.3 mol of acid.

Question B4[3 marks]

A student dilutes 50 cm³ of 2.0 mol/dm³ HCl to a total volume of 200 cm³. Calculate the new concentration.

Question B5[2 marks]

Calculate the number of moles in 75 cm³ of 0.4 mol/dm³ sodium carbonate solution.

Section C: Mass Concentration

Advanced calculations - combining g/dm³ and mol/dm³

Question C1[2 marks]

A solution contains 10 g of NaOH dissolved in 200 cm³ of water. Calculate the concentration in g/dm³.

Question C2[3 marks]

Calculate the mass of copper sulfate (CuSO₄) needed to make 500 cm³ of a solution with concentration 80 g/dm³.

Question C3[4 marks]

A solution contains 8.0 g of sodium hydroxide (NaOH) in 250 cm³. Calculate: (a) the concentration in g/dm³, (b) the concentration in mol/dm³. [Mᵣ(NaOH) = 40]

Question C4[3 marks]

A student makes 2 dm³ of glucose solution by dissolving 180 g of glucose in water. Calculate the concentration in g/dm³.

Question C5[4 marks]

A hydrochloric acid solution has a concentration of 73 g/dm³. Calculate the volume (in cm³) needed to obtain 14.6 g of HCl.

📐 Essential Formula Reference

Molar Concentration:

C = n / V

where C = mol/dm³, n = mol, V = dm³

Mass Concentration:

C = m / V

where C = g/dm³, m = g, V = dm³

Moles from Mass:

n = m / M

where n = mol, m = g, M = g/mol

Volume Conversion:

1 dm³ = 1000 cm³

Divide by 1000: cm³ → dm³

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