The mole

The mole

Author: Jose Popoff

-Express the amount of a substance in terms of mole.

-Explain the relationship between mole and Avogadro´s number and apply it to the resolution of problems.

-Calculate the molar mass of a substance.

A mole is a measurement of the amount of substance.  It is equal to 6.022 x 1023.  

1 mole = 6.022 x 1023 
This concept is easy to grasp if you relate it to the "dozen" used to express an amount of 12.  So, just like a dozen eggs (for instance) represents 12 eggs, a mole of eggs would be 6.022 x 1023 eggs.
1 mole CO2 = 6.022 X 1023 CO2 molecules
1 mole Fe = 6.022 X 1023 atoms of Fe
1 mole NaCl = 6.022 X 1023 formula units (we use the term "formula unit" here since NaCl is an ionic
                                                                               compound, therefore does not form molecules)
It is more useful, however, to express the moles of a substance in terms of its mass.  The mass of one mole of a substance is called the molar mass.  The molar mass of any substance is obtained by adding the individual masses of each component atom.
For example, the molar mass of CO2 is: 
         C ⇒ 1 (number of C atoms present in the formula) x 12.0107 g (molar mass of carbon; obtained from the periodic table.) =  12.0107 g
         O ⇒ 2 (number of O atoms present in the formula) x 15.999 g (molar mass of carbon; obtained from the periodic table.)    =  31.998 g
                                                                                                                                                                            44.0087 g

Check out the video examples below to have a better idea on how to apply these concepts.
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Example 7

Example 8- From grams to number of atoms