What mass of nitrogen is present in 5.00 mol of NH3 and N2H4?
1 mole of NH3 contains 1 mole of nitrogen atoms and 3 moles of hydrogen atoms. Therefore 5 moles of NH3 contain 5 moles of nitrogen atoms and 15 moles of hydrogen atoms. Atomic mass of nitrogen is 14 g/mol, i.e. 1 mole of N atoms has a mass of 14 g. Therefore 5 moles of nitrogen have a mass of 5 x 14 g = 70g. 1 mole of N2H4 contains 2 moles of nitrogen atoms and 4 moles of hydrogen atoms. Therefore 5 moles of N2H4 contain 10 moles of nitrogen atoms and 20 moles of hydrogen atoms. Atomic mass of nitrogen is 14 g/mol, i.e. 1 mole of N atoms has a mass of 14 g. Therefore 10 moles of nitrogen have a mass of 10 x 14 g = 140g.
