There are 252.07 grams of ammonium dichromate per mol of ammonium dichromate molecules. There are 8 atoms of hydrogen per molecule of ammonium dichromate.
Convert grams to mole of molecules. And then molecules to atoms.
55.90 / 252.07 = moles of molecules
Since there are 8 hydrogen per 1 molecule multiply this by 8.
55.90 * 8 / 252.07 = 1.77 moles of hydrogen
