Transcript molar mass
Chem 11: Finish Unit 4 start
Unit 5
5-3
Writing Formulas for Ionic
Compounds
1.
2.
3.
4.
tin (IV) sulphate
ammonium sulphate
iron (II) sulphate
Hg2+ and Cl- forms an ionic compound
Common Acids (p74)
Memorize the following:
acid
name
HCl
hydrochloric acid
H3PO4
phosphoric acid
HNO3
nitric acid
H2SO4
sulfuric acid
CH3COOH
acetic acid
Daily Question
Complete the table
Cation(C)
Anion(A)
or
Neutral (N)
Sr2+
OHNH4+
Ar
Monoatomic(M)
elements
Diatomic (D)
Triatomic (T)
or Polyatomic (P)
Charge
The
and
!
1) Words for Numbers
a “pair” of shoes
refers to 2 shoes
a “dozen” cats
refers to 12 cats
a “mole” of particles
refers to (insert large number) of molecules
1) Words for Numbers
a mole is simply just a word representing a
large number
1 mole = 6.022 x 1023
this number is often referred to as
“Avogadro’s number”
a - voe - ga - dro
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
0.5784 mol = 0.5784 x Avogadro’s Number
we abbreviate mole to mol
(similar to kilogram to kg)
0 mol = 0
2) It’s really big…
imagine a pea
it has a volume of about 0.20 cm3
how many peas would it take….?
to fill a fridge
to fill a 3 story home
1000 homes
106
1m deep across BC
1018
1m deep on all land
1m deep on entire planet
109
1012
1021
≈ to a mole
this is a large number of particles…
REMEMBER
just like a 1
equals 12
1
equals 6.022
x 1023
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
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
4) Molar Mass
molar masses are quoted in units of g/mol
g
3.2g
3.2
mol
1mol
there are 3.2 grams
in every 1 mole of substance
4) Molar Mass
here are some molar masses:
one mole of……
has a mass of…
–oxygen
16.00 g/mol
–carbon
12.01 g/mol
–helium
4.00 g/mol
4) Molar Mass
molecular weight is equivalent to molar mass!
the periodic table lists all of the molar masses
molar
masses
in
g/mol
REMEMBER
a
represents big number
is the number of grams (it’s
mass) in a mole of substance
Try It
if a dozen eggs weighs 15 g, how much
does 4 dozen eggs weigh?
15 g
= 6.0 x 10 g
4 dozen
dozen
how much does 4.0 moles of carbon weigh?
12.0 g
4.0 mol
mol
= 48 g
use this “cancellation” method to ensure you are doing it properly!
4) Molecular Mass
molecular mass is found by summing the
HO
molar mass of each atom in a molecule
for example - the molar mass of Ca(HCO3)2
2
# atoms x molar mass of atom
molecule’s molar mass
5) Calculations
a common theme of Chem 11 will be finding
mass, moles or molar mass
MEMORIZE (and understand) this:
mass
recall units of molar mass
MM
moles
MM moles mass
if you are EVER
mass
moles
MM
unsure all you need to do is
CHECK the UNITS
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
moles
mass
MM
mol
36.0g
36.0g
moles
18.0g
18.0g / mol
= 2.00 mol
it is a few extra steps, but it is worth it
when the answer comes out right!
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
Try Its
find….
mass of 0.034 mol of Li
0.034 mol
6.94 g
0.26g
mol
# atoms in 4 mol of hydrogen
6.02x1023 atoms
4.0 mol
2.4x1024 atoms
mol
mass of 0.314 mol of CO2
(12.0 + 2 16.0) g
0.034 mol
13.8g
mol
# atoms in 4 g helium
find moles helium, then convert to atoms