Potassium nitrate decomposes on heating, producing potassium oxide and gaseous nitrogen and oxygen:

Question

4KNO3(s)--> 2K2O(s) + 2N2(g) + 5O2(g)
To produce 56.6 kg of oxygen, how many (a) moles of KNO3 must be heated? (b) Grams of KNO3 must must heated?

Answer 1

Here is a worked example of a stoichiometry problem such as this one.
http://www.jiskha.com/science/chemistry/stoichiometry.html