We are asked to balance the following word equation:
potassium chlorate --> potassium chloride + oxygen
The first step would be to know the chemical formula/ formula unit for each compound/ molecule. A key aspect to remember when balancing this particular word equation is that oxygen exists in its diatomic state. Thus,
KClO3 --> KCl + O2
Next, we need to identify how many atoms of each element we have on the reactant side and the product side. This is indicated by the subscripts directly to the right of each element's symbol. No subscript indicates that there is only one atom present for that element.
K = 1
Cl = 1
O = 3
K = 1
Cl = 1
O = 2
It becomes evident that the oxygens are not balanced. Thus, we begin by balancing the oxygens so that there are 6 oxygen atoms on either side of the equation. Coefficients placed to the left of a chemical formula/ formula unit are used to increase the number of atoms of an element. A coefficient applies to all atoms within that chemical formula/ formula unit.
2KClO3 --> KCl + 3O2
Now we need two potassium atoms and two chloride atoms on the product side. Thus, the following is the final balanced equation:
2KClO3 --> 2KCl + 3O2