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Mole and Molar Mass - PowerPoint

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					Introduction to the
 Mole and Molar
      Mass
Background

• When you buy eggs you usually
             Dozen
  ask for a _______ eggs.
• You know that one dozen of any
            12
  item is ______.
  Paper


• Paper is packaged by a ream.
• A ream of paper has 500 sheets.
• Why is it useful to use units like a
  dozen or a ream?
• Scientists had to select a bigger
  unit for counting molecules of
  substances.
• The unit scientists use is called a
  MOLE.
A mole can be thought
of as a chemist's dozen
One MOLE of
anything has
602,200,000,000,000,000,000,000
items.
AVOGADRO’S
NUMBER
Symbol = NA
•6.02 x 1023

• One MOLE of anything
  has 6.02 x 10 23 items.
How many Hershey’s
Kisses make up 1
                 23
MOLE? 6.02 x 10
How many caramels
make up 10 MOLES?

   10 x [6.02 x   10 23]

     60.2 x    1023
          Or

     6.02 x    1024
Find the number of
Jolly Ranchers in 4
MOLES.
     4 [6.022 x 1023]

      24.088 x 10  23

        2.41 x 10 24
How many moles are
6.022 x 1023 atoms of
           1
sodium? _____
How many moles are
12.04 x 1023 atoms of

carbon? _____
           2


         12.04 x 1023 = 2
         6.022 x 1023
How many moles are
18.06 x 1023 atoms of

sodium? _____
          3


          18.06 x 1023 = 3
          6.022 x 1023
How many moles are
60.22 x 1023 atoms of

sodium? _____ 10


          60.22 x 1023 = 10
          6.022 x 1023
How many moles are
6.022 x 10 23 molecules

of water? _____
             1
How many moles are
12.04 x 10 23 molecules
             2
of water? _____

           12.04 x 1023 = 2
           6.022 x 1023
How many moles are
30.10 x 10 23 molecules

of water? _____
             5


           30.10 x 1023 = 5
           6.022 x 1023
Part 2
Molar Mass
• Scientists use the Periodic Table
  to determine the mass of a mole of
  atom of an element.
• For example, a mole of Iron (Fe)
  atoms would have a mass of
  55.85g.
Periodic Table
The mass of 1 mole of
Strontium (Sr) is ___ g.
                  87.62



 38
 Sr
87.62
The mass of 1 mole of
Lead (Pb) is ____ g.
              207.2


 82
 Pb
207.2
66. The mass of 1 mole of
Nickel (Ni) is ____ g.
               58.69


  28
  Ni
 58.69
The mass of 4 moles of
Strontium (Sr) is _____g.
                  350.48


            38
            Sr
           87.62
The mass of 0.5 moles of
Lead (Pb) is ____ g.
             103.6


 82
 Pb
207.2
The mass of 100 moles of
(Ni) is _____ g.
        5869.00


  28
  Ni
 58.69
Molar Mass

• Scientists also use the Periodic Table
  to determine the molar mass (formula
  weight) of compounds.
• The molar mass of the compound is
  the sum of the molar masses of the
  elements that make up the compound.
Potassium Chloride
• The molar mass of Potassium
  Chloride is:
  Potassium (K) 39.10 g/mole
  Chloride (Cl) +34.45 g/mole
                  73.55 g/mole
Potassium Permanganate

• The molar mass of KMnO4 is the
  sum of all the molar masses times
  the number of atoms of each
  element for the molecule
  (subscript).
 Potassium Permanganate
           KMnO4

• Potassium (K)   39.10 g/mole
• Manganese (Mn) 54.94g/mole
• Oxygen (O)    4[16.00 g/mole]
                 158.04 g/mole.
The molar mass of 1 mole
of Sodium Chloride
(NaCl) is____ g.
         58.44
The molar mass of 1
mole of Lead Iodide
(PbI2) is _____ g.
           461.0
 The mass of 100 moles
of Nickel Sulfide (NiS)
    9076.00
is ________ g.
The mass of 1 mole of s
Glucose (C6H12O6) is
______ g.
 180.156
The mass of 1 mole of is
Sucrose (C12H24O12 )
_______ g.
 306.31
The mass of 4 moles of
Glucose (C6H12 O6) is
_________ g.
  720.624
Mole Conversions
• In chemistry, the mole is the standard
  measurement of amount.
• However, balances DO NOT give readings
  in moles. Balances give readings in grams.
• So the problem is that, while we compare
  amounts of one substance to another using
  moles, we must also use grams, since this
  is the information we get from balances.
There are three steps to converting
grams of a substance to moles.

 1. Determine how many grams are
 given in the problem.
 2. Calculate the molar mass of the
 substance.
 3. Divide step one by step two.
The three steps above can be
expressed in the following
proportion:

  Grams                Moles
---------------   =   --------------
Molar Mass             1 Mole
Example #1 - Convert 25.0 grams
of KMnO4 to moles.
Step One: The problem will tell you how many grams are
   present. Look for the unit of grams. The problem gives us
   25.0 grams.
Step Two: You need to know the molar mass of the substance.
   The molar mass of KMnO4 is 158.034 grams/mole.
Potassium (K)          =       39.10 x 1      =        39.10 g
Manganese (Mn)         =       54.94 x 1      =        54.94 g
Oxygen (O)             =       16.00 x 4      =        64.00 g
                                         ---------------
                                                       158.04 g
Step Three: You divide the grams given by the substance's
   molar mass (25.0/158.04)

       The answer of 0.16 mole has been rounded off.
Example #2 - Calculate how
many moles are in 57.0 grams of
Mg(NO3)2
Step One: 57.0 grams are given in the text of the
  problem.
Step Two: The molar mass is 148 grams/mole.
Mg (Magnesium) =         24 x 1 =     24 g
N (Nitrogen)        = 14 x 2 =        28 g
O (Oxygen) = 16 x 6 =           96 g
Step Three: Again you divide the grams by the
  substances molar mass (57.0 g/148 g).

This answer has been rounded to 0.39 moles.
Practice
Problems
1. Calculate the moles present in:
     2.00 grams of H2O
 0.11 moles water
2. Calculate the moles present in:
     75.57 grams of KBr

      0.635 moles KBr
3. Calculate the moles present in:
    100.0 grams of KClO4

  0.72 moles KClO4
4. Calculate the moles present in:
    225.5 grams of
    Sucrose (C12H24O12)

   0.63 moles Sucrose
5. Calculate the moles present in:
     350.0 grams of
     Glucose (C6H12O6)

1.943 moles Glucose
Homework
1. Calculate the moles present in:
3.00 grams of NaCl
          .05 moles
2. Calculate the moles present in:
25.0 grams of NH3
     1.47 moles NH3
3. Calculate the moles present in:
16.0 grams of KCl
      .21 moles KCl
4. Calculate the moles present in:
30.25 grams of BeCl2

      .38 moles KCl
5. Calculate the moles present in:
175.25 grams of Li2S

     3.81 moles Li2S
6. Calculate the moles present in:
75.62 grams of CO2
     1.72 moles CO2
7. Calculate the moles present in:
56.5 grams of H2O
     3.14 moles H2O
8. Calculate the moles present in:
22.6 grams of CH3COOH

  .38 moles CH3COOH
9. Calculate the moles present in:
18.4 grams of AgCl
      .13 moles AgCl
10. Calculate the moles present
in: 68.3 grams of HCN

    2.53 moles HCN

				
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