Question

How many molecules are in 0.0740 mol NH3?

Answer 1

Number of molecules NH₃ = 4.45 x 10²²

Further explanation  

A mole is a number of particles(atoms, molecules, ions)  in a substance

This refers to the atomic total of the 12 gr C-12  which is equal to 6.02.10²³, so 1 mole = 6.02.10²³ particles  

Can be formulated :

N = n x No

N = number of particles

n = mol

No = 6.02.10²³ = Avogadro's number

mol of NH₃ = n = 0.074

So the number of molecules :

$\tt N=n\times No\\\\N=0.0740\times 6.02\times 10^{23}\\\\N=4.45\times 10^{22}$