Docstoc

The Mole_

Document Sample
The Mole_ Powered By Docstoc
					THE MOLE!
Chapter 7.1
Chemcat 13.3 :

   If I give you a balance, a single penny, and a large
    bag of pennies, could you figure out how many
    pennies are in the bag without counting them?
Big measurements… Small measurements…
                     If I use the mass of one
                      penny, I could compare
                      that to the mass of the
                      bag of pennies.

                     I could divide the bag’s
                      mass by the mass of the
                      one penny to see how
                      many pennies are in my
                      bag.
Background:
   Counting all of the pennies would take a
    very long time, and would not be
    practical.

   In Chemistry, we need to be able to count
    things even smaller than that, like atoms or
    molecules.

   To make that easier, chemists use a unit
    that can count many particles at once.
The Mole

              A mole (mol) is a unit to count the amount
               of particles in a substance.
              Particles could be atoms, molecules, ions.
              Just like grams, it is a way to measure mass.
              A mole is equal to 6.02 x 1023 particles.
              The number 6.02 x 1023 is named
               Avogadro’s number
                  In honor of Amedeo Avogadro di Quaregna.
              He studied the difference between atoms
               and molecules, but did not calculate this
               number himself.
    Representative Particle

   A representative particle is the smallest
    piece represented by a substance.
   Normally for elements
       This is an atom.
   However, some elements are found bonded
    in pairs, like O2 or H2.
       The representative particle for these elements
        would be a molecule.
Here comes some more math!
   The mole and Avogadro’s number can be used like
    conversion factors.
   1 mole = 6.02 x1023 particles/atoms/ molecules

   How many moles of magnesium is in 1.25 x 1023
    atoms of magnesium?
    How many moles of magnesium is in 1.25 x 1023 atoms of
                        magnesium?


   What you know:
     1.25 x 1023 atoms
     1 mol Mg = 6.02 x 1023 atoms Mg



    I am solving for moles of Mg.




    I get .208 mol Mg
How many moles are in 2.80 x 1024 atoms
of silicon?
   What you know:
     2.80 x 1024 atoms Si
     1 mol Si = 6.02 x 1023 atoms Si


    I am solving for moles of Si




    I get 4.65 mol Si
How many molecules are in 0.360 mol of
water?
   What you know:
     0.360 mol water
     1 mol water = 6.02 x 1023 molecules water


       I am solving for molecules of water




       I get 2.17 x 1023 molecules of water

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:6
posted:2/11/2012
language:
pages:10