Chemistry · Chapter 3: The mole

Year 11 Science · About 14 minutes with activities · Turn your sound on

Chapter 3 · The mole

100 g of dry icefrozen carbon dioxide

CO₂ moleculesfar too many to count

A dozen apples12 apples

A dozen cars12 cars

Same number: 12

Different mass

Same number of atoms

1 mol of C atoms

1 mol of H atoms

2.27 mol of CO₂in 100 g of dry ice

Chapter 3 recap

A mole is the SI unit for the amount of substance: 6.022 × 10²³ particles. Like a dozen: same number of particles, different mass.
12 g of carbon = 1 mol = 6.022 × 10²³ atoms (Avogadro’s constant). Molar mass M = the sum of the atomic masses, in g mol⁻¹ (CO₂ = 44.0, CuSO₄ = 159.7).
n = m ÷ M turns grams into moles (100 g CO₂ = 2.27 mol). m = n × M turns moles into grams (0.2 mol CuSO₄ = 31.94 g).
Next: Chapter 4 · Mole ratios and limiting reactants

How do chemists count atoms they can't see?

Chapter 3 · About 14 minutes · sound on

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