Saturday, November 20, 2010

Moooooole Conversions!

Last time we learned about molar mass, so now it's time to use it in conversions. Remember: Avogrado's number = 6.022 x 10^23 particles/mol
Remember: Put answers in the correct number of sigfigs.

1) Converting between particles <--> moles. In this conversion, we use Avogrado's number.

    a) Particles --> moles
    # of particles x                1 mol               =  # of moles
                                 6.022x10^23particles

Ex.  If there are 3.01 x 10^24 C particles, how many moles are there?
              3.01 x 10^24 C particles x                 1 mol                   = 5.00 moles of C
                                                                6.022 x 10^23 particles
    b) Moles --> particles
Another example:
If there are 0.75 mole of CO2, how many molecules are there?
       0.75 moles CO2 x    6.022 x 10^23 particles  = 4.5 x 10^23 molecules of CO2
                                                          1 mole
Now that you know how many molecules are in CO2, how many atoms of Oxygen are there?
4.5 x 10^23 molecules CO2 x   2 atoms of Oxygen     = 9.0 x 10^23 atoms of O
                                                        1 molecule of CO2

2) Converting between moles <--> grams. Remember in this type of conversion we use the molar mass.

    a) Moles--> grams
     # of moles x molar mass = # of grams
                                1 mole

Note: To find the molar mass, look at the periodic table for the atomic mass.


Ex. If there are 2.04 moles of Carbon, what is the mass?
             2.04 moles x   12.0 g   = 24.5 g of Carbon
                                      1 mole

    b) Grams --> moles
      # of grams x      1 mole      = # of moles
                                molar mass        
Ex. If there is 3.45 g of Carbon, how man moles are present?
                 3.45 g x     1 mole      = 0.288 mole of Carbon
                                     12.0 g
Another example: If there are 6.2 g of MgCl2, how many moles are present?
6.2 g x     1 mole      = 0.065 mole of Mg Cl2
                  95.3 g

Whewww, that's a lot of info..time for a chem joke!
What does Avogrado put in his hot chocolate?
Marsh-mole-ows!
KEKEKE. ;P

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