Question: how many moles of hydrogen atoms are present in 1.5 moles of water?
Answer: ( 1/4 of a mole) x (6.02 x 1023 atoms/mole) = approximately 1.5 x 1023 atoms. If you have a compound like H2O, then: one mole of water contains 6.02 x 1023 MOLECULES of water. But each molecule of water contains 2 H and 1 O atom = 3 atoms, so there are approximately 1.8 x 1024 atoms in a mole of water.