Question

Number of oxygen atoms contained in 1000g of water?

Answer 1

Your answer for the question is

Answer 2

Let's assume that the water is pure. This means that the liter of water is only composed of molecule of water H2O.
You may know that the density of water is 1,00 and its bulk density is 1,00. Thus a liter of water is composed of 1000g of water. We can write: m(H2O)=1000g
The molar mass of H2O, M(H2O) is: M(H2O)=18g.mol^-1
From those results, you can calculate the material quantity n:
n(H2O)=m(H20)/M(H2O)
n(H2O)=1000/18,0
n(H2O)=55,6 mol
You can then calculate the number of hydrogen molecules by using the Avogadro constant Na=6,022.10^23.
If Nm is the number of hydrogen molecules, Nm=Na*n(H2O)
Nm=6,022.10^23*55,6
Nm=3,35.10^25
In a liter of water, there are about 3,35.10^25 hydrogen molecules.
In order to know the number of atoms in a liter water, you have now to know how many atoms there are in an hydrogen molecule, H2O. You can see there are three atoms. In 3,35.10^25 molecules, there are:
3*3,35.10^25=1,00.10^26.
Thus in a liter of water, there are 1,00.10^26 atoms.