1. Chapter 9 Chemical Names and Formulas
9.1 Naming Ions
9.2 Naming and Writing Formulas for Ionic
Compounds
9.3 Naming and Writing Formulas for Molecular
9.4 Naming and Writing Formulas for
Acids and Bases
9.5 The Laws Governing How Compounds Form
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2. Names and Formulas of Acids
-Compound that contains one or more hydrogen atoms and produces hydrogen ions when dissolved in water.
-General formula for an acid is HnX
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3. Names and Formulas of Acids
Three rules can help you name an acid with the general formula HnX dissolved in water.
1. When the name of the anion ends in -ide, the acid name begins with the prefix hydro-,the root name of the anion has the suffix -ic and is followed by the word acid.
Therefore, HCl (X= chloride) is named hydrochloric acid.
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4. Names and Formulas of Acids
Three rules can help you name an acid with the general formula HnX dissolved in water.
2. When the anion name ends in -ite, the acid name is the root name of the anion with the suffix -ous, followed by the word acid.
Thus, H2SO3 (X = sulfite) is named sulfurous acid.
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5. Names and Formulas of Acids
Three rules can help you name an acid with the general formula HnX dissolved in water.
3. When the anion name ends in -ate, the acid name is the root name of the anion with the suffix -ic, followed by the word acid.
Thus, HNO3 (X = nitrate) is named nitric acid.
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6. Names and Formulas of Acids
These three rules for naming an acid with the general formula HnX dissolved in water are summarized in the table below.
Naming Common Acids
Anion ending
Example
Acid name
-ide
chloride, Cl–
hydro-(root name)-ic acid
hydrochloric acid
-ite
sulfite, SO3–
(root name)-ous acid
sulfurous acid
-ate
nitrate, NO3–
(root name)-ic acid
nitric acid
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7. Names and Formulas of Acids
Writing Formulas of Acids
For example, consider hydrobromic acid.
Following Rule 1, hydrobromic acid (hydro- prefix and -ic suffix) must be a combination of hydrogen ion (H+) and bromide ion (Br –).
The formula is HBr.
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8. Names and Formulas of Acids
Writing Formulas of Acids
How do you write the formula for phosphorous acid?
Using Rule 1, hydrogen ion and phosphite ion (PO33–) must be the components of phosphorous acid.
You need three hydrogen ions to balance the 3– charge of the phosphite ion.
Thus, the formula for phosphorous acid is H3PO3.
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9. Names and Formulas of Acids
Writing Formulas of Acids
Finally, what is the formula for sulfuric acid?
According to Rule 3, sulfuric acid (-ic ending) must be a combination of hydrogen ion and sulfate ion (SO42–).
The formula for sulfuric acid is H2SO4 because two hydrogen ions are needed to balance the 2– charge of the sulfate anion.
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10. Name the following compounds as acids.
Sample Problem 9.8
Naming Acids
Name the following compounds as acids.
HCl
HCN
H2SO3
H3PO3
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11. Names and Formulas of Bases
A base is generally an ionic compound that produces hydroxide ions when dissolved in water.
Bases are named in the same way as other ionic compounds—the name of the cation is followed by the name of the anion.
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12. Names and Formulas of Bases
To write the formula for a base, first write the symbol for the metal cation followed by the formula for the hydroxide ion. Then, balance the ionic charges just as you would for any ionic compound.
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13. Name the following bases. KOH Fe(OH)2 NaOH
Sample Problem 9.9
Naming Bases
Name the following bases.
KOH
Fe(OH)2
NaOH
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14. - states that any chemical compound will always contain a fixed ratio of elements by mass.
Example: Water always has the same ratio of the amount of hydrogen to oxygen
2 atoms of H : 1 atom of O
If the ratio of atoms is fixed it means that the ratio of their masses is also fixed
Law of Definite proportions:
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15. Example: NO- 1 atom of N: 1 atom of O NO2 - 1atom of N : 2 atoms of O
- states  that when two elements combine to form more than one compound, it will always be ratios of whole numbers.
Example: NO- 1 atom of N: 1 atom of O
NO2 - 1atom of N : 2 atoms of O
Law of Multiple proportions:
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