Question

Assume that your tears of joy contains 0.0050g of pure water. From that quantity of pure water how many ozone (O3) Molecules could be made?

Answer 1

Go to moles first by dividing mass by molar mass: 0.0050 g/18 g/mol = 2.78E-4 mol. Every molecule of water contains 1 oxygen atom, so 2.78E-4 mol of water contains 2.78E-4 mol of oxygen atoms. Each ozone molecule contains 3 oxygen atoms, so if you have 2.78E-4 mol of oxygen atoms, you can only make a third as many ozone molecules, so divide by 3 to get 9.27E-5 mol of ozone. We want to know how many molecules of ozone this is, so just multiply by Avogadro's number and you get 5.58E19 molecules!