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Quantitative Chemistry

Using concentrations of solutions in mol/dm

  • 3 things to know
  • Paper 1

Overview

Concentration in mol/dm³, calculating moles from concentration and volume, the mass of solute in a given volume, finding an unknown concentration from a titration, and what dilution does to concentration.

What you need to know

Answer each one before you reveal it.

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Key term

Apart from grams per cubic decimetre, in which unit can the concentration of a solution be measured?

Key term

What does a concentration of 2 mol/dm³ tell you about a solution?

Key term

How is the amount in moles of solute calculated from the concentration and the volume of a solution?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Apart from grams per cubic decimetre, in which unit can the concentration of a solution be measured?

    Model answer

    Moles per cubic decimetre, mol/dm³.

  2. 2

    What does a concentration of 2 mol/dm³ tell you about a solution?

    Model answer

    Every cubic decimetre of the solution contains 2 moles of dissolved solute.

  3. 3

    How is the amount in moles of solute calculated from the concentration and the volume of a solution?

    Model answer

    Multiply the concentration in mol/dm³ by the volume of solution in cubic decimetres.

  4. 4

    How many moles of solute are in 250 cm³ of a solution of concentration 0.2 mol/dm³?

    Model answer

    0.05 mol, because 250 cm³ is 0.25 dm³ and 0.25 × 0.2 = 0.05.

  5. 5

    What mass of sodium hydroxide is dissolved in 500 cm³ of a solution of concentration 0.1 mol/dm³? Its relative formula mass is 40.

    Model answer

    2.0 g, because 0.5 dm³ × 0.1 mol/dm³ = 0.05 mol and 0.05 × 40 = 2.0.

  6. 6

    0.25 mol of solute is dissolved and the solution made up to 500 cm³. What is its concentration in mol/dm³?

    Model answer

    0.5 mol/dm³.

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