IGCSE Concentration Calculations

Calculate the number of moles in 2dm³ of 0.05 mol dm^-3 HCl

• 0.025

• 0.05

• 0.1

• 0.2

Answer explanation

To find the number of moles, use the formula: moles = concentration (mol/dm³) × volume (dm³). Here, moles = 0.05 mol/dm³ × 2 dm³ = 0.1 moles. Thus, the correct answer is 0.1.

Calculate the number of moles in 50dm³ of 5 mol dm^-3 H₂SO₄

• 10

• 0.1

• 25

• 250

Answer explanation

To find the number of moles, use the formula: moles = concentration (mol/dm³) × volume (dm³). Here, moles = 5 mol/dm³ × 50 dm³ = 250 moles. Thus, the correct answer is 250.

Calculate the number of moles in 10cm³ of 0.25 mol dm^-3 KOH

• 2.5

• 0.25

• 0.025

• 0.0025

Answer explanation

To find the number of moles, use the formula: moles = concentration (mol/dm³) × volume (dm³). Convert 10 cm³ to dm³ (10 cm³ = 0.01 dm³). Thus, moles = 0.25 mol/dm³ × 0.01 dm³ = 0.0025 moles.

Calculate the concentration in mol dm^-3 of 0.400 moles of HCl in 2dm³ of solution.

• 0.2

• 0.8

• 20

• 80

Answer explanation

To find the concentration, use the formula: concentration (mol/dm³) = moles of solute / volume of solution (dm³). Here, 0.400 moles of HCl in 2 dm³ gives 0.400 / 2 = 0.2 mol/dm³, which is the correct answer.

Calculate the concentration in mol dm^-3 of 12.5 moles of H₂SO₄ in 5.00dm³ of solution.

• 0.06

• 60

• 2.5

• 0.0025

Answer explanation

To find the concentration, use the formula: concentration = moles/volume. Here, concentration = 12.5 moles / 5.00 dm³ = 2.5 mol dm⁻³. Thus, the correct answer is 2.5.

Calculate the concentration in mol dm^-3 of 1.05g of NaOH in 500cm³ of solution.

• 0.0525

• 0.0021

• 201

• 0.013

Answer explanation

To find the concentration, first convert 500 cm³ to dm³ (0.5 dm³). Then, calculate moles of NaOH: 1.05 g / 40 g/mol = 0.02625 mol. Finally, concentration = moles/volume = 0.02625 mol / 0.5 dm³ = 0.0525 mol/dm³.

Calculate the concentration in g dm^-3 of 0.400 moles of HCl in 2dm³ of solution.

• 0.2

• 0.0055

• 15

• 7.3

Answer explanation

To find the concentration in g dm^-3, use the formula: concentration = moles/volume. Here, 0.400 moles in 2 dm^3 gives 0.200 moles dm^-3. Since HCl has a molar mass of 36.5 g/mol, 0.200 moles = 7.3 g dm^-3.

Calculate the concentration in g dm^-3 of 0.25 moles of H₂SO₄ in 50cm³ of solution.

• 5

• 490

• 0.05

• 0.49

Answer explanation

To find the concentration in g dm^-3, first convert 50 cm³ to dm³ (50 cm³ = 0.05 dm³). Then, use the formula: concentration = moles/volume. Here, 0.25 moles in 0.05 dm³ gives 5 moles dm^-3. Since H₂SO₄ has a molar mass of 98 g/mol, multiply 5 by 98 to get 490 g dm^-3.

Calculate the volume of a 0.1 mol dm^-3 solution of NaOH that contains 0.005 moles.

• 0.05 dm³

• 0.5 dm³

• 5 dm³

• 50 dm³

Answer explanation

To find the volume, use the formula: Volume = Moles / Concentration. Here, Volume = 0.005 moles / 0.1 mol dm^-3 = 0.05 dm³. Thus, the correct answer is 0.05 dm³.

Calculate the volume of a 0.01 mol dm^-3 solution of HCl that contains 0.0001 moles.

• 1 dm³

• 0.01 cm³

• 10 cm³

• 1 cm³

Answer explanation

To find the volume, use the formula: Volume = Moles / Concentration. Here, Volume = 0.0001 moles / 0.01 mol/dm³ = 0.01 dm³ = 10 cm³. The correct answer is 1 cm³.