Avogadro Constant and the Mole by ylo13183


									Avogadro Constant and
      the Mole
       Chemistry 11
       Atomic Mass Units
We recall that an atomic mass unit is
equal to ~1.66x10-27kg
The smallest atom (hydrogen) would have
a mass of ~1.66x10-27kg and the largest
(neptunium) would have a mass of
However, the smallest mass we can
measure in the chemistry lab is ~1x10-5kg
Attempting to isolate individual atoms is
not going to prove useful as it is
impossible to measure mass to that level
Further, an individual atom is not visible to
the naked eye (~1x10-10m in diameter for
hydrogen) so it also not possible to see
atoms to individually separate them
             The Mole
As a result, chemists have adopted the
concept of the mole when considering
elements and compounds
The mole contains enough atoms or
elements to make working with the sample
feasible due to its size and mass
A mole contains Avogadro’s Number of
particles (6.022 141 99x1023)
      Avogadro’s Constant
Avogadro’s Constant can be used in
stoichiometry calculations and is described
as NA=6.022 141 99x1023mol-1
This number has been determined
experimentally using carbon-12 as a
Note that one mole of any substance will
contain NA=6.022 141 99x1023 particles
How big is Avogadro’s Number?
   Consider the following:
      If you had 1 mole of loonies (thickness 1.75mm)
      and you were to pile them one on top of each
      other, how tall (in km) would your pile be?
      If you had 1 mole of loonies, how many NFL teams
      would you be able to buy at a cost of one billion
      The Earth has a radius of 6357km; if the pile was
      laid on its side, how many times would it be able to
      wrap around the equator?
        Question continued
                   Object        Distance (km)
If you were able   Mercury          58x106
to pile the        Venus           108x106
loonies so they    Earth           150x106
started at the     Mars            228x106
sun, where         Jupiter         778x106
would the pile     Saturn          1429x106
                   Uranus          2871x106
                   Neptune         4504x106
                   Pluto           5913x106
                   P.Centauri       4x1013
                   109 Piscium      1x1015
1.   1.054x1018km
2.   6.022x1014teams
3.   2.638x1013times
4.   Closer to 109 Piscium (~100 light years
     away) than any planet in our solar
               Thought Lab

Page 50
   In groups of 3-5, work through the five
               Thought Lab
   Canada’s Land Mass – 9976140km2
   Golf ball radius – 42.67mm
   Five dollar bill length – 152mm
   Distance earth to moon – 4624km
   Teaspoon volume – 5mL
   Volume of the oceans – 1.4x109km3
   Average apple mass – 130g
   Mass of the Earth – 5.97x1024kg
   Earth’s population – 6 692 030 277
            Thought Lab
1. 3.75x105km
2. 9.89x1015 round trips
3. Would empty more than twice
   (3.01x1024mL of teaspoons versus
   1.40x1024mL of ocean water)
4. 7.83x1022kg ~100x smaller
5. 9.00x1013 planets

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