Section 2.4—Defining, Naming &
Writing Acids & Bases
We need to know how acids and bases behave when talking about ant-acids!
Acids
Acids – Arrhenius Definition
A compound that has a H+ cation that it
can donate to water to produce the
hydronium ion (H3O+1)
+1
water
+1
hydronium ion
By this definition, if an acid is to give a H+1 to water, then all
acids will have hydrogen as the cation (first element written).
How do Acids produce Hydronium?
water
acid
Hydrogen cation with some anion
How do Acids produce Hydronium?
+1
-
How do Acids produce Hydronium?
+1
Hydronium ion
Anion
Naming Acids
Naming Non-oxygen Acids
These compounds :
Start with “H” (more than 1 “H” is OK, too).
Have only 2 elements in total (One of them is
hydrogen the other is NOT oxygen.)
Examples: HCl
H2S
To name these compounds:
Use “hydro____ic acid”
Fill in the blank with the anion’s name without
the last syllable
Example #1
HBr
Example #1
It’s an acid
Hydrogen cation
HBr
Bromine
No oxygen
Use “hydro___ic”
Hydrobromic acid
Naming Oxygen Acids
These compounds have:
Start with “H” (more than 1 “H” is OK, too).
Contain a polyatomic ion that has oxygen in it.
To name these compounds:
Use “___ic acid” for “-ate” anions; the blank is
filled in with the polyatomic ions name without
the suffix.
Use “___ous acid” for “-ite” anions; the blank is
filled in with the polyatomic ions name without
the suffix.
Examples: HNO2 is . . .
HNO3 is . . .
Example #2
H2SO3
Example #2
It’s an acid
Hydrogen cation
H2SO3
Sulfite ion
“-ite” ion
Use “___ous” acid
Sulfurous acid
Example #3
H2SO4
Example #3
It’s an acid
Hydrogen cation
H2SO4
Sulfate ion
“-ate” ion
Use “___ic”
Sulfuric acid
Let’s Practice
HI
Example:
Write the name
for the following
compounds
H2CO3
HC2H3O2
H3PO3
Let’s Practice
Example:
Write the name
for the following
compounds
HI
hydroiodic acid
H2CO3
carbonic acid
HC2H3O2
acetic acid
H3PO3
phosphorous acid
Writing Acid Formulas
“Hydro-” acids
To write these formulas:
The cation is H+1
Write the anion and charge
Balance the charges by adding the appropriate
subscript to the hydrogen cation
Example #4
Hydrofluoric acid
Example #4
H+1
Hydrogen cation
Hydrofluoric acid
Only one other element
F-1
Example #4
H+1
Hydrogen cation
Hydrofluoric acid
Does not contain oxygen
F-1
H+1F-1
HF
NON “Hydro-” acids
To write these formulas:
The cation is H+1
If it is an “-ic” acid, the anion is the “-ate”
polyatomic ion
If it is an “-ous” acid, the anion is the “-ite”
polyatomic ion
Add subscript to the hydrogen cation to balance
charges
Example #5
Carbonic acid
Example #5
H+1
Hydrogen cation
Carbonic acid
From the “___ate” anion
CO3-2
Example #5
H+1
Hydrogen cation
Carbonic acid
From the “___ate” anion
CO3-2
H+CO32-
H2CO3
Example #6
Nitrous acid
Example #6
H+1
Hydrogen cation
Nitrous acid
From the “___ite” anion
NO2-1
Example #6
H+1
Hydrogen cation
Nitrous acid
H+NO2-
From the “___ite” anion
NO2-1
HNO2
Let’s Practice
Phosphoric acid
Example:
Write the
formula for the
following acids
Hydroiodic acid
Acetic acid
Perchloric acid
Let’s Practice
Example:
Write the
formula for the
following acids
Phosphoric acid
H3PO4
Hydroiodic acid
HI
Acetic acid
HC2H3O2
Perchloric acid
HClO4
Bases
Objective:
•Define and distinguish between acids & bases
•Explain and use nomenclature rules for naming
and writing formulas for bases
Bases – Arrhenius Definition
Bases produce the hydroxide ion in water
-1
Hydroxide Ion
MOST bases will be ionic compounds with
the OH-1 anion. (Ex. NaOH or Ca(OH)2)
MOST IMPORTANT EXCEPTION is NH3
(ammonia).
NH3 + H2O  NH4+1 + OH-1
Naming & Writing Bases
Naming Bases
Most bases are just ionic compounds with
“hydroxide” as their anion
The most common exception to this is
ammonia. NH3 is a base even though it
doesn’t contain “-OH” as the anion.
Example #7
NaOH
Example #7
Sodium
NaOH
Hydroxide
Sodium Hydroxide
Example #8
Iron (III) hydroxide
Fe+3
OH-1
criss –cross the number of the charges
Fe(OH)3
Let’s Practice
Ca(OH)2
Example:
Write the
formula or
name for each
KOH
Sr(OH)2
Copper (II) hydroxide
Magnesium hydroxide
Let’s Practice
Example:
Write the
formula or
name for each
Ca(OH)2
Calcium hydroxide
KOH
Potassium hydroxide
Sr(OH)2
Strontium hydroxide
Copper (II) hydroxide
Cu(OH)2
Magnesium hydroxide
Mg(OH)2