A mixture of KCI and KClO3 weighing 1.80g was heated. The dry O2 generated occupied 140ml at STP. What percent of the original mixture was KCl03?

Answer 1

You know 1 mol oxygen (32.0 grams) occupies 22.4L at STP. Convert 140 mL to grams, then,
%oxygen = (mass oxygen/mass original sample)*100 = ??%