1. The problem statement, all variables and given/known data This is a solved example problem in my chemistry book: What mass of oxygen gas O2 is liberated when a 2.5 gram sample of sodium nitrate NaNO3 is heated? Please keep in mind that I am self-studying, I am not currently in chemistry class. 2. Relevant equations 2NaNO3 ---> 2NaNO2 + O2 Known: 2.5 g NaNO3, 85 g of NaNO3/1 mole NaNO3, 1 mole O2/2 moles NaNO3, and 32 g O2/1mole O2 Unknown: mass O2 g 3. The attempt at a solution This is how it was solved: 2.5 g NaNO3 X (1 mole 3/85 g NaNO3) X (1 mole O2/2 moles NaNO3) X (32 g O2/1 mole O2) = 0.47 g O2 What I don't understand is how they got the 85 grams of NaNO3 and the 32 grams of O2????? Can someone please show me step-by-step how they got the 85 grams and the 32 grams?? Are these related to the atomic mass of each element?