Question: how many molecules are present in 1.0 kg of hydrogen gas?
Answer: Molecules of hydrogen gas are represented as . The molecular mass of hydrogen gas is 2 g/mole. To make up for 1 kg hydrogen or 1000 gm of hydrogen gas, we need 500 moles of hydrogen gas. These many moles of hydrogen gas will have atoms (500 times the Avogadro's number of atoms).