One mole of any substance contains 6.02 x 10²³ particles.
One mole of oxygen has 6.02 x 10²³ atoms
One mole of caffeine has 6.02 x 10²³ molecules
One mole of diatomic nitrogen contains two moles of nitrogen atoms. Atomic mass of nitrogen is 14 g. Thus,
Mass of diatomic nitrogen = 2 x 14 = 28 g