Don't forget to criss-cross charges.
| Unbalanced Equation | Balanced Equation |
|---|---|
| Al + O₂ → Al₂O₃ | 4 Al + 3 O₂ → 2 Al₂O₃ |
| Na + Cl₂ → NaCl | 2 Na + Cl₂ → 2 NaCl |
To predict the products, follow the decomposition pattern for the reactants:
| Decomposition Type | Example |
|---|---|
| metal carbonates decompose into metal oxide + CO₂ | CaCO₃ → CaO + CO₂ |
| metal hydroxides decompose into metal oxides + H₂O | Ca(OH)₂ → CaO + H₂O |
| metal chlorates decompose into metal chlorides + O₂ | Ca(ClO₃)₂ → CaCl₂ + 3 O₂ |
To predict the products, switch the element by itself with the positive/negative ion in the other compound.
| Equation |
|---|
| Cu + 2 AgNO₃ → 2 Ag + Cu(NO₃)₂ |
| Br₂ + 2 NaI → I₂ + 2 NaBr |
To predict the products, switch the ions in the compounds.
| Equation |
|---|
| NaCl + AgNO₃ → NaNO₃ + AgCl |
| 2 KI + Pb(NO₃)₂ → 2 KNO₃ + PbI₂ |
For a complete combustion reaction, the products are always CO₂ and H₂O.
| Unbalanced Equation | Balanced Equation |
|---|---|
| C₆H₁₄ + O₂ → CO₂ + H₂O | 2 C₆H₁₄ + 19 O₂ → 12 CO₂ + 14 H₂O |
| C₂H₅OH + O₂ → CO₂ + H₂O | C₂H₅OH + 3 O₂ → 2 CO₂ + 3 H₂O |