How many total atoms are in 0.630 g of P2O5?

Answer 1

1 mol of P2O5 has a mass of 2*31 + 5*16 = 142 g so 0.630 grams is how much of a mole? That's 0.630/142 = 0.00444 mols P2O5. 1 mole P2O5 contains 0.00444 x 6.02E23 P2O5 molecules. So number of atoms is 7 times that.