Balance real GCSE chemistry equations by changing the big numbers in front of each formula. The atom table updates as you go and turns green when each element is balanced.
The rules
- Never change the small numbers. They are part of the formula. H2O is water but H2O2 is hydrogen peroxide, a different substance. You can only change the big numbers in front.
- A big number multiplies the whole formula. 2H2O has 4 hydrogen atoms and 2 oxygen atoms.
- A small number after a bracket multiplies everything inside it. Ca(OH)2 has 1 Ca, 2 O and 2 H.
- Balance elements in compounds first. Leave elements on their own, like O2, H2 or Fe, until last because changing them affects nothing else.
- If you need half a molecule, double every number. 3½ O2 is not allowed, so 1 : 3½ becomes 2 : 7.
- Use the smallest whole numbers. A blank box means 1. If every number divides by 2, divide them all.
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