Number of Mole of Atoms and Number of Mole of Molecules

Number of Mole of Atoms and Number of Mole of Molecules

  1. All molecules contain more than one atom.
  2. For example, in a carbon dioxide molecule (CO2), there are 3 atoms – 1 carbon atom and 2 oxygen atoms.
  3. Therefore, in 5 carbon dioxide molecules, there will be 15 atoms  – 5 carbon atom and 10 oxygen atoms.
  4. Similarly,  in 1 mole carbon dioxide molecules, there will be 3 mole atoms  – 1 mole carbon atoms and 2 mole oxygen atoms, and in 3 mole carbon dioxide molecules, there will be 9 mole atoms  – 3 mole carbon atoms and 6 mole oxygen atoms, so on and so forth.
Example:
  1. How many hydrogen molecules can be made with 20 mol of hydrogen atoms?
  2. How many hydrogen atoms are there in 20 mol of hydrogen molecules?

Answer:
a. 
Each hydrogen molecules (H2) consist of 2 hydrogen atoms.
Therefore, 20 mol of hydrogen atoms can make 10 mole of hydrogen molecules.

b. Number of mole of hydrogen atoms in 20 mole of hydrogen molecules
= 2 x 20 mole = 40 mole.

Example:
  1. Find the number of carbon atom in 0.75 mol of carbon dioxide.
  2. Find the number of oxygen atom in 0.75 mol of carbon dioxide.

Answer:
a. 
Each carbon dioxide molecules (CO2) consist of 1 carbon atom and 2 oxygen molecules.
Therefore, 0.75 mole of carbon dioxide contain 0.75 mole carbon atoms.

b.
Number of mole of oxygen atoms in 0.75 mole of carbon dioxide
= 2 x 0.75 mole = 1.50 moles.