Calculate the theoretical mass percent of oxygen in KClO3.

here is the my mass percentage of 02 25gKCl03/30.0gKCl03=0.61%02.

2 answers

Close. You need to find the mass percentage of oxygen _atoms_ in the KClO3 molecule.

NB: There are 3 atoms of O in every molecule of KClO3.

KClO3: 122.5498 g/mole
Contains:
O: 3 * 15.99943 g/mole
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Mass percentage: 39.1664%
I don't really understand how you got this answer.