As you can see from the diagram above, 6.02 x 1023 is the number of atoms in one mole. When we convert between molecules and atoms, we use the subscripts.
EXAMPLES
-How many atoms are there in 1.5 mol of Iron?
1.5mol x 6.02x10^23 atom/1 mol =9.0 x 10^23
(All you do to solve this is multiply the 1.5 mol by 6.02 x 10^23)
-How many water molecules are there in 0.65mol?
0.65mol x 6.02 x 10^23 molecules/ 1 mol =3.9 x 10^23 molecules
(All you do to solve this is multiply the 0.65 mol by 6.02 x 10^23)
-How many Hydrogen atoms are there? How many Oxygen atoms?
We know, from the formula for water, that there are two Hydrogen atoms and one Oxygen atom in every molecule. So, this is our conversion unit:
3.9 x 10^23 molecules x 2 H/ 1 molecule = 7.8 x 10^23 Hydrogen atoms.
3.9 x 10^23 molecules x 1 O/ 1 molecule= 3.9 x 10^23 Oxygen atoms.
-A cylinder of Helium contains 4.6 x 10^30 atoms. How many moles of Helium is this?
4.6 x 10^30 atoms x 1mol/ 6.02 x 10^23 atoms = 7.6 x 10^6 moles of Helium
-A sample of Zinc Sulphate contains 5.0 x 10^22 atoms of Oxygen. How many moles of Oxygen is this? How many moles of Zinc Sulphate (ZnSO4) are there?
5.0 x 10^22 x 1mol/ 6.02 x 10^23 atoms = 0.083 mol of Oxygen
0.083 mol Oxygen x 1 ZnSO4/4 O= 0.021 mol of ZnSO4
-A glass contains 5.0 mol of vinegar (CH3COOH). How many molecules are there in the glass?
5.0 mol x 6.02 x 10^23 molecules/ 1 mol = 3.0 x 10^24 molecules of vinegar
-How many Carbon atoms are there?
3.0 x 10^24 molecules x 2 C/1 molecule= 6.0 x 10^24 atoms of Carbon
-How many Hydrogen atoms are there?
3.0 x 10^24 molecules x 4 H/1 molecule= 1.2 x 10^25 atoms of Hydrogen
-How many Oxygen atoms are there?
3.0 x 10^24 molecules x 2 O/1 molecule= 6.0 x 10^24 atoms of Oxygen
-How many atoms are there in total?
6.0 x 10^24 atoms of Carbon + 1.2 x 10^25 atoms of Hydrogen + 6.0 x 10^24 atoms of Oxygen = 2.4 x 10^25 atoms in total
Mr. Doktor in slow motion!
Next time: Multistep Moles Conversions!
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