Balancing a Chemical Equation
The process of adjusting the coefficients in a chemical equation so that the number of atoms of each element is equal on both sides. Only coefficients can be changed — formulae cannot.
Worked example: Unbalanced: H₂ + O₂ → H₂O Count atoms: Left — 2H, 2O. Right — 2H, 1O. Oxygen is not balanced. Balanced: 2H₂ + O₂ → 2H₂O Check: Left — 4H, 2O. Right — 4H, 2O. ✓
State Symbols
Letters written in brackets after each formula in a chemical equation to show the physical state of each substance. (s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous — dissolved in water.
Example: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)