Download Chapter 7 - Chemical Quantities

Ch. 7 Pg. 1
Chapter 7 - Chemical Quantities
Recall all learning maps so far.
To this point........ we’ve only looked at “chemistry”
occurring at the “atomic and molecule level”.
However, in reality the matter we see is made up of huge
quantities of atoms or molecules, just like how the ocean is
made up of drops of water.
We are used to measuring things in grams, kg, L, m, etc.
How can we tell how many atoms/molecules are in 1g, 1L or
1 m of the material?
Amedeo Avogadro, an italian physicist, discovered that if
you count the number of particles in
atomic/molecular
weight of that material, you will get exactly the same number
of particles. This number is
6.022136736 x 10 23
with only 3 sig. fig. It wold be
It is called Avogadro’s number!!
Ch. 7 Pg. 2
So what his discovery really means is that:
12 g of C = 6.02 x 10 23 atoms of carbon
g of Au = 6.02 x 10 23 atoms of gold
g of H2O = 6.02 x 10 23 molecules of water
g of salt (NaCl) = 6.02 x 10 23 molecules of salt
What if we give an unit to this quantity, what should we call
it?
We know that
1 dozen egg = 12 eggs
1 quarter = 25 cents
1 molecular weight of matter = 6.02 x 10 23 molecules
1 mole = 1 molecular weight = 1 molar mass
1 mole = 1 atomic weight = 1 molar mass
1 mole of matter = 6.02 x 10 23 molecules
Ch. 7 Pg. 3
1 molar mass of matter = 6.02 x 10 23 molecules
We can use the quantity “mole” to calculate number
of particles in a certain mass, and vice versa.
This “mole” concept can be used for
Anything
1 mole of students = 6.02 x 10 23 students
1 mole of chickens = 6.02 x 10 23 chickens
1 mole of cars = 6.02 x 10 23 cars
How many moles of students U of L has?
Q. 7.7b) How many atoms of Cl in 2.0 mole of PCl3?
Ch. 7 Pg. 4
Q. 7.5c) slightly altered from book
How many atoms in 0.025 moles of C20H24N2O2?
Q. 7.8c) How many moles of C2H6O contain
5.0 x 10 24 atoms of H?
Ch. 7 Pg. 5
Recall
1 mole =
molar mass
How to find molar mass?
e.g. molar mass for carbon?
- for an element in its’ MOLECULAR form, the molar
mass in grams is equal to atomic mass X #atoms in
molecule
e.g. molar mass for molecular oxygen?
- for a compound, the molar mass in grams is equal to
the sum of atomic mass X #each atom
e.g. molar mass for phosphoric acid
?
Ch. 7 Pg. 6
Q. 7.26 How many moles of C are in each of the
following?
0.25 mole of C2H6?
5.0 x 10 24 molecules of CO2?
Ch. 7 Pg. 7
Empirical Formula vs Molecular Formula
(EF)
(MF)
MF = C2H6
MF = C6H12O6
MF = CO2
EF =
EF =
EF =
Empirical Formula and %Composition
e.g. What is the percent composition of C, H and O
is glucose?
MF = C6H12O6
EF = CH2O
Ch. 7 Pg. 8
e.g. A compound was analysed by elemental analysis
and found to contain 58.01% C, 16.23% H and
25.76% O. What is the empirical formulae?
Ch. 7 Pg. 9
Mole Relationships in Chemical Equations
( STOICHIOMETRY
and
CONSERVATION OF MASS)
CH 4 + 2 O 2
1 mole of
needs
to give
and
CO 2 + 2H 2 O
moles of
mole of
moles of water.
e.g. If we burn 100 grams of methane with enough
oxygen, how much CO2 will be produced
assuming complete reaction?
Ch. 7 Pg. 10
Q. 7.47 If we assume 100% reaction......
NH 3 + O 2
N 2+ H 2O
a) How many grams of O2 are needed to react with
8.0 moles of NH3?
b) How many grams of N2 can be produced with
6.50 g of O2?
Ch. 7 Pg. 11
c) How many grams of H2O are formed from the
reaction of 34 g of NH3?
Ch. 7 Pg. 12
Percent Yield
Theoretical Yield
versus
Actual Yield
Q. 7.51
C 3H 8 + O 2
CO 2 + H 2 O
Calculate the mass of CO2 that can be produced if the
reaction of 45.0 g of propane and sufficient oxygen has a
60% yield.
Chapter 7 Learning Map