1. The and !
Molar Mass
Mole

2. 1) Words for Numbers a “pair” of shoes a “dozen” cats
refers to 2 shoes
a “dozen” cats
refers to 12 cats
a “mole” of particles
refers to (insert large number) of molecules

3. 1) Words for Numbers HUGE!
a mole is simply just a word representing a large number
1 mole = x 1023
this number is often referred to as “Avogadro’s number”
HUGE!
pronounced: a
- ga
- voe
- dro

4. we abbreviate mole to mol (similar to kilogram to kg)
REMEMBER
a mole is just a really really big number!
6.02 x 1023
1 mol = Avogadro’s Number
4 mol = 4 x Avogadro’s Number
mol = x Avogadro’s Number
we abbreviate mole to mol (similar to kilogram to kg)
0 mol = 0

5. 2) It’s really big… x 250 imagine a pea how many peas would it take….?
it has a volume of about 0.20 cm3
how many peas would it take….?
to fill a fridge
106
to fill a 3 story home
109
1000 homes
1012
1m deep across BC
1018
1m deep on all land
1021
x 250
1m deep on entire planet
≈ to a mole
this is a large number of particles…

6. REMEMBER
dozen
just like a equals 12
equals x 1023
M O L E

7. 3) Why? why bother with a new unit? what’s easier to say:
3 moles atoms
1.807 x 1024 atoms
that’s a pretty good reason

8. 4) Molar Mass atoms and molecules have mass
we measure numbers of particles using the mole
a mole of atoms will have a mass
this mass is called the molar mass

9. 4) Molar Mass molar masses are quoted in units of g/mol for example:
there are 3.2 grams
in every 1 mole of substance

10. 4) Molar Mass has a mass of… here are some molar masses: one mole of……
oxygen
carbon
helium
has a mass of…
16.00 g/mol
12.01 g/mol
4.00 g/mol

11. 4) Molar Mass molecular weight is equivalent to molar mass!
the periodic table lists all of the molar masses
molar
masses in
g/mol

12. REMEMBER MOLE molar mass a represents big number
is the number of grams (it’s mass) in a mole of substance
molar mass

13. Try It if a dozen eggs weighs 15 g, how much does 4 dozen eggs weigh?
how much does 4.0 moles of carbon weigh?
= 48 g
use this “cancellation” method to ensure you are doing it properly!

14. 4) Molecular Mass sometimes called Molecular Weight (MW)
molecular mass is found by summing the molar mass of each atom in a molecule
for example - the molar mass of Ca(HCO3)2
H2O
# atoms x molar mass of atom
molecule’s molar mass

15. if you are EVER unsure all you need to do is
5) Calculations
a common theme of Chem 11 will be finding mass, moles or molar mass
MM: round this value to 1 decimal place  don’t worry about sig figs here!
MEMORIZE (and understand) this:
recall units of molar mass
! ! !
if you are EVER unsure all you need to do is
CHECK the UNITS
! ! !

16. 5) Calculations
for ALL CALCULATIONS I want to see you CANCELLING UNITS!
example: how many moles are in 36.0 g of H2O?
MM = 18.0 g/mol
mass = 36.0 g
= 2.00 mol
it is a few extra steps, but it is worth it
when the answer comes out right!

17. Remember a mole is just a large number of particles
consider the following chemical reaction:
2 H2 (g) + O2 (g)  2 H2O (l)
you can now describe this as:
2 molecules of hydrogen react with a molecule of oxygen to produce 2 molecules of water
or equally well as
2 mol of hydrogen react with 1 mol of oxygen to produce 2 mol of water

18. Try Its More mass of 0.034 mol of Li # atoms in 4 mol of hydrogen
find….
mass of mol of Li
# atoms in 4 mol of hydrogen
mass of mol of CO2
# atoms in 4 g helium
find moles helium, then convert to atoms