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

First, I don't believe for a minute that KNO3 decomposes on heating to produce K2O, N2 and O2; however, we can calculate whatever we wish.
Convert 56.6 kg oxygen to moles. Moles = grams/molar mass.

Using the coefficients in the balanced equation, convert moles oxygen to moles KNO3. That's part a.

For part b, convert moles KNO3 to grams. grams = moles x molar mass.

Answer 2

.3mol

b.404g

Answer 3

3.5375