Question: how many molecules are in 2.0 moles of chlorine gas?
Answer: A mole is a unit of measurement, which equals 6.02 * 10^23. If you have a mole of cl2, then you have 6.02 * 10^23 molecules of cl2. If you want to calculate for atoms however, you can see that each molecule has two atoms of cl. Therefore you have 2* 6.02 * 10^23 chlorine atoms.