The MOLE

you may think that a mole is a small furry blind creature who lives underground and looks something like this.....
cute right?
but we're talking chemistry so its not as simple as all that. For us the mole is a number that represents a huge number of particles. 6.02* 1023 particles, to be exact. But why do we even need a number to represent particles? Couldn't we just weigh and measure individual particles?

Here's the problem: atoms, molecules, and other particles are really small.

ex.  Helium has an atomic mass of 4.0 atomic mass units, but how much does one helium atom weigh in grams? The answer is an incredibly small amount, not very practical for day to day calculations.

So to fix that, a really smart, really old guy came up with an answer. This guy's name was Amadeo Avagadro and he came up with this number in 1811!  Here's his head shot.

Avagadro said, what if  4.0 grams of Helium contains a number of atoms? And what if this number of atoms is constant for all elements and compounds, depending on their atomic mass? According to Avagadro, 12 grams of Carbon, 4 grams of Helium, and 11 grams of Sodium would each have 6.02*1023 atoms.

There are 3 different conversions we usually do with Avagadro's number.

1. A sample of sodium has 5.6*1026 atoms. How many moles of sodium is this?

      5.6*1026 x 1 mol           = 9.3 mol
                       6.02*1023

2. 15 moles of chlorine equals how many atoms?
 
     15 x   6.02*1023 = 9* 1024
               1 mol
3. Or the opposite of number 1, which is how many molecules are in 3.09 moles of NaCl?

   3.09 mol x 6.02*1023 = 1.86*1024
               1 mol

These are the 3 different conversions you might need to do with the Mole.

oh and here's another mole: