Question: how many moles of hydrogen are there in?
Answer: Using the periodic table, we can get the atomic mass, which tells you how many grams of hydrogen is in 1 mole. In this case, the periodic table tells us there is 1g of hydrogen per mole. We know that dihydrogen (H2) has 2 hydrogen atoms per molecule, so there will be 2 * 1g hydrogen per mole = 2g dihydrogen per mole.