The number of moles that are 1.50 x10^23 molecules of NH3 are
=0.249 moles
calculation
The number of moles is calculated using Avogadro's law constant
that is According to Avogadro's law
1 moles of a substance = 6.02 x10^23 molecules
? moles = 1.50 x10^23 molecules
by cross multiplication
= [( 1.50 x 10^23 molecules x 1 moles) / (6.02 x10^23)] = 0.249 moles