Question

Find the number of atoms in 4.35g of NH_{​​​​​3}? And also find its mass ratio with hydrogen gas I.e H_{​​​​​2}?

Answer 1

The molecular mass of NH3 is 14+3 = 17
so one mole of NH3 would be 17 gms.
We have 4,35g of NH3, so we have 4.35/17 mole molecules
now 1 mole = 6.023 x 10^23 molecules
therefore 4.35/17 mole = 4.35/17 *( 6.023*10^23) molecules
= 4*4.35/17*(6.23*10^23) atoms [as 1NH3 contains 4 atoms]
= 1.0235*6.23*10^23 atoms
= 6.38*10^23 atoms

N2 + 3H2 = 2NH3
Here 2 moles of NH3 are formed per 3 moles of H2,

mass of H2 = (4.35/2*17) *(3moleH2/1moleH2)*2g of H2 =0.767g

Mass ratio of NH3 with H2 = 4.35 : 0.767 = 5.671 : 1 Ans