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 6.5108
 0.0000000100 is 1.0010-8
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 3.00108
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
 6.71108 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 6.0221023 (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