Concentration in mol/dm³ (Higher Tier)

This lesson covers how to calculate concentration in mol/dm³ and convert between g/dm³ and mol/dm³, as required by the AQA GCSE Combined Science Trilogy specification (8464) at Higher tier. This builds on the g/dm³ concentration work from the previous lesson.

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What Is Concentration in mol/dm³?

While g/dm³ tells you the mass of solute per unit volume, mol/dm³ tells you the number of moles of solute per unit volume. This is more useful for chemists because reactions depend on the number of particles, not their mass.

$\text{concentration (mol/dm}^3) = \frac{\text{moles of solute}}{\text{volume of solution (dm}^3)}$concentration (mol/dm3)=volume of solution (dm3)moles of solute​

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The Two Concentration Triangles

Triangle 1: mol/dm³

graph TD
    A["<b>moles of solute</b>"] --- B["<b>concentration (mol/dm³)</b>"]
    A --- C["<b>volume (dm³)</b>"]
    B --- C
    style A fill:#f59e0b,color:#000,stroke:#d97706
    style B fill:#3b82f6,color:#fff,stroke:#2563eb
    style C fill:#3b82f6,color:#fff,stroke:#2563eb

To Find	Formula
Concentration (mol/dm³)	$c = \dfrac{n}{V}$c=Vn​
Moles	$n = c \times V$n=c×V
Volume (dm³)	$V = \dfrac{n}{c}$V=cn​

Triangle 2: g/dm³ (reminder)