Question

A sample of ammonia has a mass of 51 g. How many molecules are in this sample?

Answer 1

m(NH₃)=51g, n(NH₃)=m/M=51g÷17g/mol(14+3×1)=3mol
N(NH₃)=n×Na(Avogadro number)=3mol×6·10²³1/mol=18×10²³ molecules