The balanced chemical reaction is:
2NaClO3 9= 2NaCl + 3O2
We are given the amount of sodium chlorate to heat. This will be the starting point of our calculations.
200 g NaClO3 (1 mol / 106.44 g) ( 3 mol O2 / 2 mol NaClO3) (32 g O2 / 1 mol O2) = 90.19 g O2