Capture all of the smoke and weight it. it will weigh exactly the same before and after you burn it but will just be CO2 and H2O gas.
2KClO3 --> 2KClO2 + O2
12 6 (moles)
The ratio of KClO3 and O2 is 2:1. This means 2 moles of KClO3 can create 1 mole of O2. So 12 moles of KClO3 will create 6 moles of O2.
Answer:
112 mL
Explanation:
The formula for percent by volume is

If you have 250 mL of a solution that is 44.8 % v/v,

I think its 3 precipitation.