chemistry
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9.5
The Laws Governing Formulas and
Names
A birthday cake for a fouryear-old has four candles.
The ratio of candles to
birthday cake is 4:1. In
chemistry, similar
relationships exist among
the masses of elements as
they combine in
compounds.
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9.5
The Laws Governing
Formulas and Names
>
The Laws of Definite and Multiple
Proportions
The Laws of Definite and Multiple
Proportions
What are the two laws that describe
how compounds form?
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9.5
The Laws Governing
Formulas and Names
>
The Laws of Definite and Multiple
Proportions
The rules for naming and writing formulas for
compounds are possible only because
compounds form from the elements in
predictable ways.
These ways are summed up in two
laws: the law of definite proportions
and the law of multiple proportions.
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9.5
The Laws Governing
Formulas and Names
>
The Laws of Definite and Multiple
Proportions
The Law of Definite Proportions
The law of definite proportions states that in
samples of any chemical compound, the masses
of the elements are always in the same
proportions.
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9.5
The Laws Governing
Formulas and Names
>
The Laws of Definite and Multiple
Proportions
Water obeys the law of definite proportions. In
every sample of water, the mass ratio of oxygen
to hydrogen is always 8:1.
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9.5
The Laws Governing
Formulas and Names
>
The Laws of Definite and Multiple
Proportions
Hydrogen peroxide obeys the law of definite
proportions. The mass ratio of oxygen to
hydrogen is always 16:1.
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9.5
The Laws Governing
Formulas and Names
>
The Laws of Definite and Multiple
Proportions
The Law of Multiple Proportions
The law of multiple proportions: Whenever
the same two elements form more than one
compound, the different masses of one element
that combine with the same mass of the other
element are in the ratio of small whole numbers.
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9.5
The Laws Governing
Formulas and Names
>
The Laws of Definite and Multiple
Proportions
A Diagram of the Law of Multiple Proportions
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SAMPLE PROBLEM 9.1
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SAMPLE PROBLEM 9.1
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SAMPLE PROBLEM 9.1
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SAMPLE PROBLEM 9.1
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Practice Problems for Sample Problem 9.1
Problem Solving 9.34
Solve Problem 34 with
the help of an interactive
guided tutorial.
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9.5
The Laws Governing
Formulas and Names
>
Practicing Skills: Naming Chemical
Compounds
Practicing Skills: Naming Chemical
Compounds
How do you use a flowchart to write the
name of a chemical compound?
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9.5
The Laws Governing
Formulas and Names
>
Practicing Skills: Naming Chemical
Compounds
Follow the arrows and answer the
questions on the flowchart to write the
correct name for a compound.
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9.5
The Laws Governing
Formulas and Names
>
Practicing Skills: Naming Chemical
Compounds
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9.5
The Laws Governing
Formulas and Names
>
Practicing Skills: Naming Chemical
Compounds
CuSO4 is an example from the flowchart. The
compound will end in -ite or -ate. Cu is not part of
Group A, so you must name the ions and use a
Roman numeral to identify the charge of the
transition metal. The name is copper(II) sulfate.
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9.4
The Laws Governing
Formulas and Names
>
Practicing Skills: Naming Chemical
Compounds
Practicing Skills: Writing Chemical
Formulas
What four guidelines should you follow
to write the formula of a chemical
compound?
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9.5
The Laws Governing
Formulas and Names
>
Practicing Skills: Naming Chemical
Compounds
In writing a chemical formula from a chemical
name, it is helpful to remember the following
guidelines.
An -ide ending generally indicates a
binary compound.
An -ite or -ate ending means a
polyatomic ion that includes oxygen is
in the formula.
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9.5
The Laws Governing
Formulas and Names
>
Practicing Skills: Naming Chemical
Compounds
Prefixes in a name generally indicate
that the compound is molecular.
A Roman numeral after the name of a
cation shows the ionic charge of the
cation.
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9.5
The Laws Governing
Formulas and Names
>
Practicing Skills: Naming Chemical
Compounds
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Section Quiz 9.5.
Assess students’ understanding of the
concepts in Section 9.5.
Continue to:
-or-
Launch:
Section Quiz
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Section Quiz 9.5.
1. The law of definite proportions states that
in samples of any chemical compound,
the elements are always in the same
proportion by
a. mass.
b. volume.
c. group number.
d. period number.
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Section Quiz 9.5.
2. You want to write the chemical formula for
iron(II) chloride. Based on Figure 9.22, after
identifying symbols, what is the correct next
step in the flowchart?
a. Group A elements
b. Roman numerals
c. Balance charges
d. Polyatomic ions
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Section Quiz 9.5.
3. Using the flowchart in Figure 9.20, if you
determine that the name of an ion ends in -ite
or -ate, the ion is a
a. polyatomic cation.
b. polyatomic anion.
c. transition metal cation.
d. group A anion.
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The Laws Governing
Formulas and Names
>
Concept Map
Concept Map 9 Solve the Concept Map with
the help of an interactive guided tutorial.
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END OF SHOW