Avagadro's Number and the Mole:

As we know, atoms and molecules are extremely small and microscopic objects contain too many of them to count or weigh individually. 

However, Amedeo Avogadro proposed a solution to this problem...

• the # of atoms in 12.00000 g of Carbon would be equal to a constant (this is = to 1 mole of carbon).
• this value is now called Avagadro's # and forms the basis of all quantitative chemistry

 So what is Avagadro's #?

1 Mole = 6.02 x 10^23


But What's a Mole?  

A mole is simply a multiple of things  

• 1 pair = 2
• 1 dozen = 12
• 1 century = 100  years
• So... 1 mole = 6.02 x 10^23              

How Big is a Mole?

• 1 mole of meters would cross the entire galaxy!
• $mole would be enough to give every person on earth 1 million billion dollars

You can also identify 1 mole as 602 000 000 000 000 000 000 000... 

                                                                             
Particle                                                                 
Atom:         Element            6.02 x 10^23
                                                 1 mole        Fe     
Molecule:   Covalent           6.02 x 10^23
                   Compound            1 mole        CO2  
Formula      Ionic                6.02 x 10^23
Unit:           Compound            1 mole        NaCl 

^ Example of using the mole:

• A sample of Carbon contains 3.78 x 10^24 atoms.  How many moles of carbon is this?

1. 3.78 x 10^24 atoms x 1 mole / 6.02 x 10^23 atoms
2. 3.78 x 10^24 / 6.02 x 10^23 (when doing this equation on your calculator you want to press "2nd ," which gives you EE.  This replaces the 10 and gives you a more precise answer)
3. this equation cancels out the unit atoms leaving us with the amount of moles...
4. thus your final answer is 6.28 moles

Another Example:

• Say you have 15.25 moles in a compound.  But you want to know the amount of molecules in the substance.  How would you solve this problem? 

1. 15.25 moles x 6.02 x 10^23/ 1 mole 

• But how did we figure our the ratio of molecules to moles?  You look at the chart above the first example!  Simple as that.  

    2.  15.25 moles x (6.02 x 10^23)... don't forget to use the "2nd ," instead of "x 10"
    3.  this equation cancels out the unit for moles and leaves you with the amount of molecules in the 
         substance 
    4.  your final answer is 9.1805 x 10^24 molecules