How many total atoms are there in 66.3 g of water (H2O)?

Question

How many total atoms are there in 66.3 g of water (H2O)?

Answer 1

The molecular wt of H₂0 is 18 (16+2=18), which means 1 mole of H₂O weighs18 grams. Therefore, 66.3 g of H₂O is equivalent to 66.3/18 = 3.68 moles.

Now, one mole of H₂O has an Avogadro number of molecules in it, and since each molecule is 3 atoms, three times Avogadro number of atoms. So, 3.68 moles of H₂O has 3*3.68*6.02*10^23 = 6.64 * 10^24 atoms.