An equation is balanced when there are the same number of atoms of each type on both sides of the equation.
An equation can only be balanced by putting numbers in front of formulas – you cannot change the formula itself.
Equations can be written with state symbols: (s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous (dissolved in water).
How to balance an equation:
a) Calculate how many atoms of each type are on each side of the equation.
b) If the numbers are the same then the equation is balanced.
c) If the numbers are not the same, then numbers are put in front of the formulas (this adds more of that substance). You cannot change the formulas (this would make a different substance). Hint – start with unbalanced elements that only appear in one substance on each side of the equation.
d) Keep doing this until the equation is balanced. e.g. CH4 + O2 → CO2 + H2O
Get a spare piece of paper and try to balance the following:
Ca + O2 → CaO
Na2O + H2O → NaOH
Al + O2 → Al2O3
Na + Cl2 → NaCl
Na2CO3 → Na2O + CO2
K + O2 → K2O
C4H8 + O2 → CO2 + H2O
Fe2O3 + HCl → FeCl3 + H2O
F2 + KBr → KF + Br2
C5H12 + O2 → CO2 + H2O
NH3 + O2 → NO + H2O
HNO3 → NO2 + H2O + O2
thanks to www.chemsheets.co.uk for the questions and resources