Download Chapter 7 - U of L Class Index

Ch7-p1
Chapter 7 - Chemical Quantities
To this point........
C8H18 +
we’ve only looked at “chemistry”
occurring at the “molecule level”.
O2
CO2
+
H 2O
Example question:
Carbon dioxide is a suspected greenhouse gas. The
increase in the burning fossil fuels over the last century
combined with deforestation have resulted in increased
atmospheric CO2. Theses increased levels cause sunlight
to be trapped resulting in increased temperatures.
You spend $45.00/week on gasoline (C8H18) in your
car. The cost of the gasoline is 69.9¢/L and gasoline has a
density of 0.68 g/mL. How much CO2 in kilograms do
you produce during a one year period?
How do we solve this?
Ch7-p2
Enter..............
“The MOLE”
What is this “MOLE thing”?
Where do we start...
AMU (atomic mass unit)
12
C
6
So lets weigh out 12 AMU of carbon.
We need something we can weigh.
The “MOLE” —
defined as the number of particles (ie. atoms) of
carbon-12 required to equal exactly 12 g
Amedeo Avogadro.........
6.022136736 x 1023 “particles” of carbon-12 = 12 g
So what can we measure in moles?
Ch7-p3
Anything
1 mole of carbon
=
6.02 x 1023 atoms of carbon
1 mole of gold
=
6.02 x 1023 atoms of gold
1 mole of methane
= 6.02 x 1023 molecules of methane
1 mole of sucrose
=
6.02 x 1023 molecules of sucrose
1 mole of chickens
=
6.02 x 1023 chickens
1 mole of cars
=
6.02 x 1023 cars
Q. 7.7b)
How many atoms of Cl in 2.0 mole of PCl3?
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 1024 atoms of H?
Ch7-p4
Molar Mass
- defined as the mass of one mole of a substance in grams.
- for an element in its’ ATOMIC form, the molar mass in
grams is equal to atomic mass shown on the periodic table
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 an compound, the molar mass in grams is equal to
the sum of atomic mass X #each atom
e.g.
molar mass for quinine (C20H24N2O2)?
H
CH3O
H
N
OH
H
N
Ch7-p5
Q. 7.26 How many moles of C are in each of the
following?
0.25 mole of C2H6?
5.0 x 1024 molecules of CO2?
Empirical Formula vs Molecular Formula
(EF)
(MF)
MF = C2H6
MF = C6H12O6
MF = CO2
EF =
EF =
EF =
?
Empirical Formula
e.g.
?
and
?
%Composition
What is the percent composition of C, H and O
is glucose?
MF = C6H12O6
EF = CH2O
Ch7-p6
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?
Mole Relationships in Chemical Equations
( STOICHIOMETRY
and
CONSERVATION OF MASS)
CH4 + 2 O2
e.g.
CO2 + 2 H2O
If we burn 100 grams of methane with enough
oxygen, how much CO2 will be produced
assuming complete reaction?
Ch7-p7
Q. 7.47
If we assume 100% reaction......
NH3 +
O2
N2 +
H2O
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 when
6.50 g O2?
c) How many grams of H2O are formed from the
reaction of 34 g of NH3?
Percent Yield
Theoretical Yield
versus
Actual Yield
Q. 7.51
C3 H 8
+
O2
CO2 +
H2O
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.