How many atoms of NH_{​​​​​3} are present in 4.25 grams of NH_{​​​​​3.}

Molar mass NH3 = 14+3 = 17g/mol
given mass = 4.25g
no of moles = 4.25/17 = 0.25 mol of NH3

1 mol of NH3 contains 6.022×10^23 molecules
0.25 mol NH3 contains 0.25×6.022×10^23 = 1.5055×10^23 molecules

1 molecule of NH3 contains 4 atoms
Number of atoms in 1.5055×10^23 molecules = 4×1.5055×10^23 atoms.

Tanswer is = 6.022×10^23 atoms