Calculate the number of ammonia molecules in 3.9 g.

•3.9g of ammonia
•molar mass of ammonia = 17.03g/mol

1st you have to covert grams to moles by dividing the mass of ammonia with the molar mass:

(3.9 g)/ (17.03g/mol) = 0.22900763mols

Then convert the moles to molecules by multiplying it with Avogadro’s number:

Avogadro’s number: 6.022 x 10^23

0.22900763mols x (6.022 x 10^23 molecs/mol)
= 1.38 x 10^23 molecules