A balanced equation has the same number of each kind of atom on both sides, and, for ionic equations, the same total charge. An independent check means testing the equation by a method different from the one you used to balance it. That way a slip in your balancing is not repeated in your checking.
This skill supports formulas and equations and every calculation that uses a ratio. It is the third lesson of the extended explanation and error repair module.
What is the checking routine?
Use these steps in order.
- Check the formulas first. A wrong formula cannot be fixed by coefficients.
- Atom count: for each element, coefficient × subscript, added for every substance on that side. Write both totals.
- Charge count for ionic equations: coefficient × charge, added on each side.
- Mass count (optional but strong): total Mr × coefficients on the left equals the total on the right.
- Lowest whole numbers: if every coefficient can be divided by the same number, simplify.
Worked example
Equation to check: Fe₂O₃ + 3CO → 2Fe + 3CO₂
Atom count:
| Element | Left | Right |
|---|---|---|
| Fe | 2 | 2 |
| O | 3 + 3 = 6 | 3 × 2 = 6 |
| C | 3 | 3 |
All three match. The equation is balanced.
Mass count: Mr: Fe₂O₃ = 2 × 56 + 3 × 16 = 160, CO = 28, Fe = 56, CO₂ = 44. Left: 160 + 3 × 28 = 244. Right: 2 × 56 + 3 × 44 = 112 + 132 = 244. The masses agree.
Charge count example (ionic): Zn + 2H⁺ → Zn²⁺ + H₂. Left charge: 0 + 2 × (+1) = +2. Right charge: +2 + 0 = +2. Equal. Atoms: Zn 1 and 1, H 2 and 2. Balanced.
The mistake to watch for
Mistaken equation: 2Al + 3O₂ → Al₂O₃
A student counted aluminium (2 and 2) and stopped.
The oxygen count shows the problem: left 3 × 2 = 6, right 3. The equation is not balanced. The fix is coefficients only: 4Al + 3O₂ → 2Al₂O₃.
Check the fix: Al 4 and 2 × 2 = 4, O 3 × 2 = 6 and 2 × 3 = 6. Balanced.
Stopping after the first element is the most common way a wrong equation survives. Count every element, and do not skip the one that looks easy.
Check yourself
Use the atom count on each, then open the answer.
1. Is C₃H₈ + 5O₂ → 3CO₂ + 4H₂O balanced?
Show answer
C: 3 and 3. H: 8 and 4 × 2 = 8. O: 5 × 2 = 10 and 3 × 2 + 4 = 10. Yes, balanced.
2. Is the ionic equation Cu²⁺ + Fe → Cu + Fe³⁺ balanced? If not, correct it.
Show answer
Atoms match (1 each), but charge is +2 on the left and +3 on the right. Not balanced. Iron forms Fe²⁺ in this reaction, so the correct equation is Cu²⁺ + Fe → Cu + Fe²⁺ (+2 on both sides).
3. Find the coefficients: __Fe + __O₂ → __Fe₂O₃
Show answer
4Fe + 3O₂ → 2Fe₂O₃. Check: Fe 4 and 2 × 2 = 4, O 3 × 2 = 6 and 2 × 3 = 6.
Where this leads next
With a trustworthy equation, go on to connecting observation, model and conclusion. The equation balance reasoning trainer shows an atom table as you try coefficients, and the mixed practice set has equation checks in it.
If you keep fixing one element and breaking another, a teacher in online one-to-one Chemistry tuition can show you which element to balance first and why.