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Unit 5
Day 1
The Mole
What is a mole?
I have some examples on the front table
Our text says: a mole (mol) of a substance represents 6.02 X 1023
representative particles of that substance.
Wikipedia says: The mole is a unit of measurement for the amount of substance or
chemical amount. It is one of the base units in the International System of Units, and
has the unit symbol mol
What this means is that the mol is a word that stands for a number, like the word dozen stands for
the number 12. A mol of something has 6.02 X 1023 representative particles of that substance.
1 mol of X = 6.02 X 1023 representative particles (atoms, molecules, formula units, ions) of X
Looks like we could make a conversion factor out of that !!!!! (Yipee)
1) One billion Pb atoms is how many mols of Pb?
2) How many Hydrogen atoms are in 0.5 moles of sucrose (C12H22O11)
What is different about a dozen cars and a dozen eggs?
What is the same?
What is different about a mol of water molecules and a mol of Pb atoms?
What is the same?
But why 6.02 X 1023?????
To answer that we need another term(s):
gram atomic mass (if its and atom)
gram molecular mass (if it’s a molecule)
gram formula mass (if its ionic)
molar mass (generic term for all of the above)
EX: What is the molar mass of the following:
1) Pb
2) Water
3) Calcium chloride
4) C12H22O11
But wait…don’t those numbers look familiar?
ADD ‘EM UP!
Unit 5
Day 1
The Mole
That’s right, now we know something much more valuable:
The molar mass of something is the mass of 1.0 mol of that stuff in grams; just like adding
up the atomic masses gives us the mass of just one of them in amu’s.
Pb’s molar mass is 207.2
1 atom of Pb has a mass of 207.2 amus
1mol of Pb (6.02 X 1023 Pb atoms) has
a mass of 207.2 grams
Review and try molar masses:
1)
2)
H2O’s molar mass is 18, therefore:
3)
1 molecule of H2O has a mass of 18 amus (1+1+16)
1 mol of H2O (6.02 X 1023 molecules of H2O) has a mass of 18 grams
or 1 mol H2O = 18 g H2O (I feel more math coming on)
4)
EX:
How many mols of water are in 47.9 g of water?
5)
6)
7)
How many molecules of water is that?
8)
9)
How many molecules of water are in 47.9 g of water?
(the above in one step)
One mole of X is:
 6.02 X 1023 of X (in number)
 Has a mass in grams = the molar mass of X
 If X is a gas at STP has a
volume = 22.4 L
Convert the following to mols:
1) 12. 8 g of sodium acetate
2) 8.0 L of dinitogen pentoxide gas at
STP
3) 1.7 X1019 water molecules
How many molecules and what is the mass
of 150.0 mL of carbon dioxide at STP?
10)
MOLE MAP