How many atoms of oxygen are present in 4.5 g of water?

Answer 1

4.5 g x (6.022 x 1023 molecules / 18.0 g) x (1 atom Oxy / molecule)

= 1.5055 x 1023 atoms of Oxygen

Answer 2

There are 4.5 g of water, which is composed of 2 hydrogen atoms and 1 oxygen atom. The molecular weight of water is approximately 18 g/mol, so there would be approximately 0.25 mol of water in 4.5 g. Since each molecule of water has 1 oxygen atom, there are approximately 0.25 mol of oxygen atoms in 4.5 g of water, which is about 1.5 x 10^22 atoms of oxygen.