Calculate the moles of aluminum ions present in 250.0 g aluminum oxide. Acetaminophen, a common aspirin substitute, has the formula C8H9NO2. Determine the number of molecules acetaminophen in a 500-mg tablet. Determine the number of oxygen atoms present in 25.0 g of carbon dioxide. the density of lead (pb) is 11.3 g/cm3. calculate the volume of 1 mol of Pb.