Question

How many miles of O2 can be produced by letting 12.00 miles of KC103 react?

Answer 1

 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.