Moles

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Moles
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Mole

• A small blind burrowing furry rodent
• A spy
• A skin condition
• 6.02 x 10 23

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Mole

• A small blind burrowing furry rodent
• A spy
• A skin condition
• 6.02 x 10 23

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6.02 x 10 23

• is called Avogadros Number
• and a Mole

This is COLLECTIVE NOUN
What is the collective noun name for 12?
A dozen
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Working with collective nouns

• A Dozen is easy to work with because the number
  12 is a small number.
• Two dozen 2 x 12 24
• A half dozen 12/2 6
• 163.67 dozen ????
• 163.67 x 12 1964.04
• (lots of eggs, or donuts or whatever!)

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Working with collective nouns

• A Mole is easy to work with because the number
  6.02 x 10 23 is a number.
• Two moles 2 x (6.02 x 10 23 ) 12.04 x 1023
• A half mole (6.02 x 10 23 )/2 3.01 x 1023
• 163.67 moles ????
• 163.67 x (6.02 x 10 23 ) 985.3 x 1023
• (lots and lots of eggs, or donuts or
  whatever!)

fun
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Review Working with exponents

• 2 x (6.02 x 10 23 ) 12.04 x 1023
• 1.204 x 1024
• 163.67 x (6.02 x 10 23 ) 985.3 x 1023
• 9.853 x 1025

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Where did the Mole come from?

• A Mole is defined as the number of atoms of
  Carbon in 12.000 grams of carbon.
• (did somebody really count these out?)

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Why 12 grams of Carbon?

• Remember The amu is based on Carbon-12
• One carbon atom has a mass of 12 amu
• But who can work with one carbon atom???

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Why 12 grams of Carbon?

• It just so happens that
• One carbon atom has a mass of 12 amu
• One MOLE of carbons atoms has a mass of 12 grams
• Grams are easy to work with !

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But this magic doesnt just work for Carbon!

• The atomic mass (in grams) of any atom is the
  mass of one MOLE of that element
• The gram formula mass of any compound is the mass
  of one MOLE of that compound

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Since chemists are unbelievably lazy.

• MOLE
• is often abbreviated as
• MOL

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Moles and GFM

• Since the gram formula mass is the mass of one
  mole, we can write this mathematically as
• GFM grams per mole
• grams/mole
• grams
• mole

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Moles and GFM

• So,
• for Na, with a GFM of 23 g
• There are 23 grams per mole of Na
• 23 grams/mole
• 23 grams
• mole

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Moles and GFM

• So,
• for NaCl, with a GFM of 58 g
• There are 58 grams per mole of NaCl
• 58 grams/mole
• 58 grams
• mole

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Converting grams to Moles

• This formula is in Table T
• of moles given mass
• gram formula mass

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Converting grams to Moles

• of moles given mass
• gram formula mass
• How many moles of Na are in 333 g of Na?
• of moles 333g
• 23g/mole
• of moles 14.48 g/g/mole
• 14.48 moles

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You try it!

• How many moles are there in 678 grams of NaCl?

GFM of NaCl 23 35.5
58.5g/mol
of moles 678 grams
GFM
of moles 678 grams NaCl
58.5 g/mol
11.6 mole NaCl
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Converting Moles to Grams

• This formula is NOT in Table T, but you can get
  it by rearranging the grams to mole formula
• Grams of moles x GFM
• Grams of moles x grams
• mole

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Converting Moles to Grams

• Grams of moles x GFM
• How many grams are there in 6.37 moles of Na?
• Grams 6.37 moles x 23 grams Na
• mole
• Grams 147 grams Na

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You try it!

• Grams of moles x GFM
• How many grams are there in 106.8 moles of NaCl?

Grams 106.8 moles x 58.5 grams/mol
6248 grams NaCl
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Mole Relationships in chemical equations

• A recipe calls for
• 2 cups flour
• 4 eggs
• 1/2 cup chocolate chips

• To make double the amount
• 4 cups flour
• 8 eggs
• 1 cup chocolate chips

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Mole Relationships in chemical equations

• A recipe calls for
• 2 cups flour
• 4 eggs
• 1/2 cup chocolate chips

• To make half the amount
• 1 cups flour
• 2 eggs
• 1/4 cup chocolate chips

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You can write this as a chemical reaction (all
cooking is!)

• 2 cups flour 4 eggs ½ cup chips 1
  cake
• 2 4 .5
  1
• These numbers show the RATIOS of ingredients in
  the recipe that make it come out right
• If you know the correct ratios, you can double,
  triple or halve the recipe easily.

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• 2 cups flour 4 eggs ½ cup chips 1
  cake
• 2 4 .5
  1

Suppose you only have 3 eggs ? How much flour
will you need?
4 eggs (original recipe) 3 eggs (new recipe)
2 cups flour (original recipe) X cups
flour (new recipe)
Cross multiply and solve for x
X 1.5 cups flour
X 6 4
4X 2x3
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• 2 cups flour 4 eggs ½ cup chips 1
  cake
• 2 4 .5
  1

Suppose you only have 3 eggs ? How many cups of
chips will you need?
4 eggs (original recipe) 3 eggs (new recipe)
.5 cups chips (original recipe) X cups
chips (new recipe)
Cross multiply and solve for x
X .375 cups chips
X 1.5 4
4X .5 x 3
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• 2 cups flour 4 eggs ½ cup chips 1
  cake
• 2 4 .5
  1

Suppose you only have 3 eggs ? How many cakes can
you make?
4 eggs (original recipe) 3 eggs (new recipe)
1 cake (original recipe) X cakes (new
recipe)
Cross multiply and solve for x
X .75 cakes
X 3 4
4X 1 x 3
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In balanced chemical equations..

• the coefficients in front of the formulas can be
  interpreted two ways
• as numbers of molecules (easy to visualize)
• Or
• As number of moles (practical in the lab)

4 NH3 5O2 4NO 6H2O
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How many moles of water will be produced if 3
moles of ethane are burned?

• 2 C2H6 7 O2 4 CO2 6 H2O
• 2 7 4 6
  (original)

3 ? ?
X (new)
2 moles ethane (original) 3 moles ethane (new)
6 moles water (original) X moles water (new)

2X 3 x 6 X 18/2 X
9 moles water
You try How many moles of carbon dioxide will be
produced? How many moles of oxygen
gas will be needed?