Question

Number of atoms in 4.25 g of NH3is approximatly............

Answer 1

=>Molar mass NH3 = 14+3*1 = 17g/mol 

4.25g = 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 = 1.5*10^23 molecules .

1molecule of NH3 comtains 4 atoms 

Number of atoms in 1.5*10^23 molecules = 6*10^23 atoms. 

The correct answer is 6*10^23 atoms.

...........................................Hope this ans helps.