Moles in Solutions (Concentration)

This lesson covers how to calculate concentration and relate it to moles, mass and volume. These calculations are essential for GCSE Chemistry and are required by the Edexcel specification (1CH0). Concentration in mol/dm³ is a Higher tier topic.

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What Is Concentration?

Concentration tells you how much solute is dissolved in a given volume of solution.

• A concentrated solution has a large amount of solute in a small volume.
• A dilute solution has a small amount of solute in a large volume.

Concentration can be expressed in two ways:

1. g/dm³ (grams per cubic decimetre) — Foundation and Higher
2. mol/dm³ (moles per cubic decimetre) — Higher only

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Volume Conversions

Before doing concentration calculations, you must be confident converting between units of volume:

Unit	Abbreviation	Relationship
Cubic centimetre	cm³	1 dm³ = 1000 cm³
Cubic decimetre	dm³	1 dm³ = 1 litre
Litre	L	1 L = 1000 mL = 1000 cm³

To convert cm³ to dm³: divide by 1000

To convert dm³ to cm³: multiply by 1000