Mole

 Just as:  one dozen  =  12 things      or     one gross  =  144 things

                So:  one mole  =  6.02 x 10²³ things

What chemical quantities contain one mole, or 6.02 x 10²³ things?

1)  The formula weight (molecular weight), in grams, of a substance contains one mole, or 6.02 x 10²³ particles.

   Example: 

                    H  =  1 gram  =  1 mole  =  6.02 x 10²³ atoms H

                    H₂  =  2 grams  =  1 mole  =  6.02 x 10²³ molecules H₂

                CO₂  =  44 grams  =  1 mole  =  6.02 x 10²³ molecules CO₂

2)  22.4 liters of a gas at STP (0^oC & 1 atm of pressure) contain one mole, or 6.02 x 10²³ particles.

   Example:

        22.4 liters of NH₃ gas (17 grams)  =  1 mole  =  6.02 x 10²³ molecules

Guide Sheet to Mole Problems