1. The problem statement, all variables and given/known data 4Al + 3O2 = 2Al2O3 What number of O-atoms will react if 45dm3 of the gas reacts with an excess of Al? The answer is apparently: 4 atoms 2. Relevant equations 3. The attempt at a solution Using the formula n=V/Vn (or the law stating that any gas occupies 22.4dm3 at STP), I found that the number of moles was (225/112) or 2.01. Then I used the formula: n=n*Na (number of moles times Avagadro's Constant) giving me 1.24*1024 atoms. Where did I go wrong please?