Transcript CHE 117A
CHE 117A
Review and Refresh
Review and Refresh
Every Substance is composed of
atoms
An atom is the smallest possible
particle of a substance
Atoms are extremely small
Review and Refresh
In most substances atoms
combine to form molecules
A molecule is a combination of
two or more atoms held together
in a specific shape by attractive
forces
Review and Refresh
A substance that contains only
one type of atom is called and
element.
O
Oxygen
Na
Sodium
Br
Bromine
Sn
Tin
Review and Refresh
Elements combine to form
compounds
The relative amounts of the
elements in a compound never
change
This ratio is shown in the
chemical formula of the compound
O2, H2O, CO, CH4
Review and Refresh
Review and Refresh
The elements can be grouped
according to their physical and
chemical properties
Periodic table
Metals on the left
Nonmetals on the right
Review and Refresh
Review and Refresh
Elements combine to form
compounds which can exist in
three different phases
Solid, liquid, and gas
Review and Refresh
Changes between phases are
physical changes
The substance’s chemical nature
remains the same
Ice melting to water
Water converting to steam
Sugar dissolving in water
Chemical changes involve one
substance becoming another
substance
C burning in O2 to form CO2
Review and Refresh
Scientific Notation
650,000,000 is 6.5108
0.0000000100 is 1.0010-8
Review and Refresh
Units
G
M
k
c
m
µ
n
p
=
=
=
=
=
=
=
=
giga = 109
mega = 106
kilo = 103
centi = 10-2
milli = 10-3
micro = 10-6
nano = 10-9
pico = 10-12
Review and Refresh
Unit conversions
Example 1: The speed of light is
generally accepted to be 3.00108
m/s. What is the speed of light
in mph?
1 mile = 5280 ft
2.54 cm = 1 in
3.00 108 m 60 s 60 min 100 cm
1 in
1 ft
1 mile
s
1 min
1 hr
1m
2.54 cm 12 in 5280 ft
6.71108 mph
Review and Refresh
Three temperature scales
°F, °C, K
°F = 1.8°C + 32
K = °C + 273.15
Review and Refresh
Precision describes the
exactness of a measurement
Accuracy describes how close a
measurement is to the true
value
Review and Refresh
Example 2: Significant Figures
3.52 10 7.154 10
2
6
6.125
1 .5
2.52 10
4.1
13.24 1.435 5.6 20.3
5
Review and Refresh
Back to molecules…
The chemical formula describes
the composition of a substance
for most elements, the formula is
the chemical symbol
seven diatomic elements: H2, N2, O2,
F2, Cl2, Br2, I2
also, P4 and S8
Review and Refresh
When to different elements
combine to form a binary
compound, the chemical formulas
are written as follows
Usually the element farther to
the left on the periodic table is
written first
KCl, Al2O3, Mg3N2
Review and Refresh
H is only written first when
combined with elements from
Groups 6 and 7
H2O, HCl
NaH, B2H6, CH4
If the elements are in the same
group, the lower element is
written first
SeO2, IF3
Review and Refresh
Example 3:
Write the correct chemical
formulas for the following sulfur
compounds
Review and Refresh
SO3
H2S
SF4
S2F2
Review and Refresh
Chemical formulas only give the
ratio of elements in a compound
they say nothing about the
arrangement of the elements
relative to each other
Structural formulas give both
Propane, C3H8
Review and Refresh
Often two very different
compounds have the same
chemical formula
C2H6O
Review and Refresh
We can also represent
structural formula in 3D
ball-and-stick model
space-filling model
Review and Refresh
Review and Refresh
We can simplify line structures
even further
C-H bonds are not drawn
C is not labeled
C always has 4 bonds
Review and Refresh
Review and Refresh
Review and Refresh
Review and Refresh
Example 4:
Write the chemical formula for
the following compounds
C2H4Cl2
C4 H8 O2
C3 H4 O
Review and Refresh
Naming Compounds: binary
compounds
Elements that appear first keep
their name
Second element is named with the
root name plus –ide
Use greek prefixes to represent
number of atoms
never use mono- for the first
element
Review and Refresh
CO
carbon monoxide
NO2
nitrogen dioxide
SO3
sulfur trioxide
P4O10
tetraphosphorus pentoxide
Review and Refresh
Ionic compounds are named with
the cation first and the anion
second
Memorize Table 3.5
NaCl
sodium chloride
NH4NO3
ammonium nitrate
Review and Refresh
If the compound has a
transition metal then the
charge of the metal is
indicated in the name by a
Roman numeral
FeCl3
iron(III) chloride
Cu2O
copper(I) oxide
Review and Refresh
The mole
a mole of any substance is equal
to 6.0221023 (NA) items of that
substance
exactly like a dozen eggs
Obviously we can’t count that
many items
so we count mole by mass
Review and Refresh
12g of carbon-12 contains
exactly one mole of atoms
all other molar mass are based on
this value
the atomic mass on the periodic
table is the mass in grams of one
mole of the element
Review and Refresh
The molar mass of a compound is
simply the sum of the atomic
masses of the constituent
elements
Example 5:
What are the molar masses
(molecular weights) of NaCl and
C3H8
58.44 g/mol and 44.10 g/mol
Review and Refresh
Example 6:
How many moles of NH4NO3 are
contained in 16.5 g of the
compound?
NH 4 NO3 80.04 g/mol
1 mol
16.5 g NH 4 NO3
0.206 mol NH 4 NO3
80.04 g
Review and Refresh
Suggested Problems
Chapter 1
8, 10, 12, 26, 33, 34, 40, 41, 55,
61, 69, 87, 88, 98
Chapter 3
2, 5, 8, 9, 10, 15, 16, 24, 31, 35,
38, 41 – 43, 72, 81, 95, 101, 108