[Dark*Phantom]

Answer to questions 1 and 2
Each mole of NH4 contains one mole of nitrogen because no numbers are written after nitrogen
Example: One mole of H2SO4 contains 2 moles of hydrogen, one mole of sulphur and 4 moles of oxygen

Answer to question 3
Let's suppose that the mass of the compound in 100g
Mass of oxygen = 63 gm
Mass of nitrogen = 37 gm
Molar mass of oxygen = 16 gm
Molar mass of nitrogen = 14 gm
No. of moles in oxygen = 63 / 16 = 3.9375 moles
No. of moles in nitrogen = 37 / 14 = 2.643 moles
The ratio between nitrogen and oxygen = 2.643 : 3.9375 = 1 : 1.5 = 2 : 3

The empirical formula is N2O3

Answer to question 4
No. of moles in carbon = 0.02
No. of moles in hydrogen = 0.04
Ratio between carbon and hydrogen =0.02 : 0.04 = 1:2

The empirical formula is CH2