1 What a balanced equation tells us

• A balanced symbolic equation fixes the proportions in which substances react and form.
• The coefficients give moles (and, for gases, volumes in the same ratio, and particles in the same ratio).
• From it we can calculate:

1. masses of substances,
2. numbers of moles,
3. numbers of particles,
4. volumes of gases,
5. the limiting reactant (Lesson 4).

For example 2H₂O(l) → 2H₂(g) + O₂(g) (electrolysis of acidified water) states: 2 mol of water give 2 mol of hydrogen and 1 mol of oxygen; in terms of mass, 36 g of water give 4 g of H₂ and 32 g of O₂ (conservation of mass: 36 = 4 + 32); in terms of particles, 2 molecules of water give 2 molecules of H₂ and 1 of O₂.