Question

The number of molecules in 4.25 gram of ammonia approximately is

Answer 1

Molar mass NH3 = 14+3 = 17g/mol 
4.25g = 4.25/17 = 0.25 mol NH3 

1mol = 6.022*10^23 molecules 
0.25 mol = 0.25*6.022*10^23 
Number of molecules = 1.51*10^23 molecules NH3

Answer 2

Molar mass of ammonia is 17g and 17g ammonia contains 6.022×10^23 number of ammonia molecules due to this 4.25 g ammonia will contain (6.022×10^23×4.25)/17 = 1.5×10^23 number of ammonia molecules.

Molar mass NH3 = 14+3 = 17g/mol , 4.25g = 4.25/17 = 0.25 mol NH3 , 1mol = 6.022*10^23 molecules , 0.25 mol = 0.25*6.022*10^23  and the Number of molecules = 1.51*10^23 molecules NH3