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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 = giga = 109
M = mega = 106
k = kilo = 103
c = centi = 10-2
m = milli = 10-3
µ = micro = 10-6
n = nano = 10-9
p = 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
mph 106.71
ft 5280
mile 1
in 12
ft 1
cm 2.54
in 1
m 1
cm 100
hr 1
min 60
min 1
s 60
s
m1000.3
8
8
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
26 10154.71052.3 51052.2
5.1
125.61.4
6.5435.124.13 3.20
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 C4H8O2 C3H4O
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?
3434
34
NONH mol 0.206g 80.04
mol 1NONH g 16.5
g/mol 80.04NONH
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