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Chemistry · Chapter 4: Mole ratios and limiting reactants

Year 11 Science · About 15 minutes with activities · Turn your sound on

Chapter 4 · Ratios and limiting reactants
2 bread + 1 cheesemakes 1 toastie
Cheese runs outlimiting
Bread left overin excess
Particle boxeach particle = 0.1 mol

Chapter 4 recap

  • Mole ratio: the ratio of moles of reactants and products in a balanced chemical equation. Read it from the numbers in front: 2Mg + O₂ → 2MgO is 2 : 1 : 2. Balance first.
  • Unknown over known: moles wanted = (its ratio number ÷ known ratio number) × moles known. N₂ + 3H₂ → 2NH₃: 0.6 mol H₂ → 2/3 × 0.6 = 0.4 mol NH₃.
  • Limiting reactant: completely used up; sets the maximum product. Excess reactant: not used up. 1.2 mol Mg + 0.8 mol O₂ → Mg limiting, 1.2 mol MgO, 0.2 mol O₂ left.
  • Next: Chapter 5 · Acids, bases and solutions

If you run out of one ingredient, how much can you make?

Chapter 4 · About 15 minutes · sound on

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