HELP!! I need help with CHEM~?

Question

If a KClO3/KCl mixture weighing 1.63 g loses 0.368 g upon heating, what is the % KClO3 in the mixture?

Answer 1

I don't have the references handy, but assuming all the lost weight is oxygen, you use atomic weights to determine how mich KClO3 would contain 0.368g of oxygen. That mass divided by 1.63g is your percent.