Question

How many total atoms are in 0.450 grams of P2O5

Answer 1

First, we need to figure out the molar mass of P2O5. 

P x 2: 30.97g x 2 = 61.94g
O x 5: 16.00g x 5 = 80.00g
                           + 141.94g

0.450g x 1 mole/141.94g = 0.00317 moles = 3.17 x 10^3 moles

Now we are going to use Avogadro's number (=6.02 x 10^23)

(3.17 x 10^3 moles) x (6.02 x 10^23 atoms) / (1 mole) = 1.91 x 10^27 atoms