Question: how many hydrogen atoms are there in 4 moles of water?
Answer: There are two hydrogen atoms per water molecule. There are 6.022x10^23 water molecules per mole. To calculate for 5 moles, (2 H atom)/(H2O molecule) X (6.022x10^23 H2O molecules)/(mole) X 5 moles = 6.022x10^24.