Session 1:
The Chemical Formula
and Moles
Tom Hsu, PhD.
Manos Chaniotakis, PhD.
Marina Dang, PhD.
Copyright © 2012 Chaniotakas and Hsu
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Essential questions
What do these symbols and diagrams mean?
Objectives
• Identify the number of moles of each constituent element
from a chemical formula, molecular model, or structural
diagram.
•
Interpret a chemical formula and build a 3D model from it.
•
Write a chemical formula given a structural diagram.
•
Draw a structural diagram from a 3D model.
•
Create possible structures from a given chemical formula.
TEKS
8 (A) define and use the concept of a mole;
8 (B) use the mole concept to calculate the number of atoms,
ions, or molecules in a sample of material;
8 (C) calculate percent composition and empirical and
molecular formulas.
Assessment
• How many moles of chlorine are there in one mole of CCl4?
• If you have six moles of oxygen, how many moles of acetic acid
(C2H4O2) could you produce assuming you had an unlimited
supply of carbon and hydrogen?
• What is the chemical formula for a compound containing 1 mole
of magnesium, 2 moles of oxygen, and 2 moles of hydrogen?
• Build and draw three possible ways in which 3 moles of carbon,
8 moles of hydrogen, and 2 moles of oxygen could be divided
into one or more compounds.
Molecules
Molecular models
• Each ball represents both
one atom and one mole of
atoms
• Colors represent different
kinds of atoms (elements)
• The grey “sticks” represent
bonds between atoms
The CPK color code
Use this
code to
assign the
color of
each
element
The CPK color code
All molecular
modeling
programs use
some variation of
this color code.
Wikipedia
Complete the table
Use a
periodic
table to
write in the
element
symbols
for each
“atom” in
the kit.
Making a molecule
Choose 5 atoms
and connect them
with bonds.
At least two
should be the
same color –
therefore the same
element.
Writing a chemical formula
Use the boxes to
describe the
elements in your
molecule.
Write 1 where there is a
single atom.
Writing a chemical formula
Transfer the
information to a
chemical formula.
Use element symbols and
subscripts to specify the
number of atoms of each
element in the molecule
Writing a chemical formula
Single atoms do not need a
subscript.
The 1 is inferred to mean a
single atom.
The structural diagram
The chemical formula does not specify the connections.
The structural diagram uses element symbols connected by
lines.
The structural diagram
When possible, draw your structural
diagrams with the lines at 90 degrees
or 120 degrees.
Chemical formula rules
Is this written H4C or CH4?
Chemical formula rules
Is this written H4C or CH4?
Carbon is often written first
in a carbon-containing
compound (organic)
Chemical formula rules
Which is the preferred way to write the
chemical formula for methanol?
Chemical formula rules
Which is the preferred way to write the
chemical formula for methanol?
The second is better because the OH
grouping makes this an alcohol and this
spelling clearly identifies the OH.
What do the models mean?
What does one
of the colored
balls represent?
What do the models mean?
What does one
of the colored
balls represent?
Is it one atom?
Is it 1,000,000
atoms?
The mole
Each ball represents two things:
1. How atoms of oxygen are connected to
other atoms in a specific compound.
2. One mole of oxygen atoms.
The size of atoms
Atoms are so small that they cannot
be measured individually.
There are more than
1,000,000,000,000,000,000,000,000
atoms in a thimble of water.
A mole
1.01 grams of hydrogen
contain 6 x 1023 atoms.
This number is called a mole.
Think of each plastic ball as
representing one mole of that
element.
Atomic masses
The periodic table lists the atomic
mass, in grams, of one mole of
each element.
Mass of one mole
How many moles of methane
contain 1 mole of carbon?
A molecule of methane
contains one carbon and
four hydrogen atoms.
Write its chemical formula
and draw its structural
diagram.
1 mole of methane contains 1
mole of carbon.
How many moles of
hydrogen are in one
mole of methane?
How many moles of
carbon?
What is the ratio of
hydrogen atoms to
carbon atoms?
How many moles of
hydrogen are in one
mole of methane? 4
How many moles of
carbon? 1
What is the ratio of
hydrogen atoms to
carbon atoms? 4/1
How many moles of oxygen are
contained in 1 mole of methanol?
Build this molecule
with one carbon, one
oxygen, and four
hydrogen atoms.
Write its chemical
formula and draw its
structural diagram.
1 mole of oxygen is contained in
1 mole of methanol.
How many moles of
hydrogen are in one
mole of methanol?
How many moles of
carbon?
What is the ratio of
carbon atoms to oxygen
atoms?
1 mole of oxygen is contained in
1 mole of methanol.
How many moles of
hydrogen are in one
mole of methanol? 4
How many moles of
carbon? 1
What is the ratio of
carbon atoms to oxygen
atoms? 1/1
How many moles of carbon are
contained in 1 mole of ethanol?
Build this molecule
with two carbon, one
oxygen, and six
hydrogen atoms.
Write its chemical
formula and draw its
structural diagram.
2 moles of carbon are contained in
1 mole of ethanol.
How many moles of
hydrogen are in one
mole of ethanol?
How many moles of
carbon?
What is the ratio of
hydrogen atoms to
oxygen atoms?
How many moles of
hydrogen are in one
mole of ethanol? 6
How many moles of
carbon? 2
What is the ratio of
hydrogen atoms to
oxygen atoms? 6/1
How many moles of carbon are in
1 mole of Pentadecylcatechol
Main constituent of urushiol the irritant oil that is
created by poison ivy.
How many moles of carbon are in
1 mole of Pentadecylcatechol
Main constituent of urushiol the irritant oil that is
created by poison ivy.
The subscript tells
you the number of
moles of each
element in 1 mole of
the compound.
Build a compound containing 2 moles of carbon, 2 moles of
oxygen, and 4 moles of hydrogen.
Build a compound containing 2 moles of carbon, 2 moles of
oxygen, and 4 moles of hydrogen.
This is one possible solution – acetic acid.
Build TWO compounds that together contain 2 moles of carbon,
2 moles of oxygen, and 4 moles of hydrogen. The compounds
may be identical or different from each other.
Build TWO compounds that together contain 2 moles of carbon,
2 moles of oxygen, and 4 moles of hydrogen.
This new compound is
the preservative
formaldehyde. Very
different from acetic acid!
Build TWO compounds that together contain 2 moles of carbon,
2 moles of oxygen, and 4 moles of hydrogen.
This new compound is
the preservative
formaldehyde. Very
different from acetic acid!
This coefficient tells us there
are two moles of this
compound.
4 moles of hydrogen, 2 moles of oxygen, and 2 moles of carbon.
Two moles of formaldehyde,
a toxic preservative.
One mole of acetic acid,
the sour flavor in lemons.
4 moles of hydrogen, 2 moles of oxygen, and 2 moles of carbon.
These are different substances even though they
contain the same elements in the same proportions!
Assessment
• How many moles of chlorine are there in one mole of CCl4?
Assessment
• How many moles of chlorine are there in one mole of CCl4?
4 moles since the subscript of chlorine is four.
Assessment
• If you have six moles of oxygen, how many moles of acetic acid
(C2H4O2) could you produce assuming you had an unlimited
supply of carbon and hydrogen?
Assessment
• If you have six moles of oxygen, how many moles of acetic acid
(C2H4O2) could you produce assuming you had an unlimited
supply of carbon and hydrogen?
One mole of acetic acid uses two moles of oxygen. That means
six moles of oxygen could produce three moles of acetic acid.
Assessment
• What is the chemical formula for a compound containing 1 mole
of magnesium, 2 moles of oxygen, and 2 moles of hydrogen?
MgO2H2
Assessment
• Draw three possible ways in which 3 moles of carbon, 8 moles
of hydrogen, and 2 moles of oxygen could be divided into one or
more compounds.
There are other possibilities.
Assessment
There are other possibilities.
Ethanol
Carbon dioxide
Oxygen
Methane
Methane
Formaldehyde
Ethylene
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