Section 2.4—Defining, Naming &
Writing Acids & Bases
We need to know what acids behave when talking about ant-acids!
Acids
Acids – Arrhenius Definition
Produce Hydronium ion (H3O+1) in water
Hydronium ion is water + a hydrogen
cation
+1
+1
water
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 have:
Start with “H” (more than 1 “H” is OK, too).
Do not contain oxygen
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).
Do contain oxygen
To name these compounds:
Use “___ic acids” for “-ate” anions
Use “___ous acids” for “-ite” anions
Do not use “hydro” with these…the word “acid” is how you know it
begins with hydrogen, not “hydro-”
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
HCl
Example:
Write the name
for the following
compounds
HNO3
H2S
H3PO3
Let’s Practice
Example:
Write the name
for the following
compounds
HCl
Hydrochloric acid
HNO3
Nitric acid
H2S
Hydrosulfuric 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
Does not contain oxygen
F-1
Example #4
H+1
Hydrogen cation
Hydrofluoric acid
Does not contain oxygen
H+1F-1
F-1
+1 + -1 = 0
HF
The compound is neutral.
Subscripts are not needed
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
H+CO32+1 + -2 = -1
Carbonic acid
From the “___ate” anion
CO3-2
H2CO3
H+H+CO32+1 + 1 + -2 = 0
Example #6
Nitrous acid
Example #6
H+1
Hydrogen cation
Nitrous acid
From the “___ite” anion
NO3-1
Example #6
H+1
Hydrogen cation
Nitrous acid
H+NO2-
From the “___ite” anion
NO3-1
HNO2
+1 + -1 = 0
Let’s Practice
Phosphoric acid
Example:
Write the
formula for the
following acids
Hydroiodic acid
Carbonous acid
Perchloric acid
Let’s Practice
Example:
Write the
formula for the
following acids
Phosphoric acid
H3PO4
Hydroiodic acid
HI
Carbonous acid
H2CO2
Perchloric acid
HClO4
Bases
Bases – Arrhenius Definition
Bases produce the hydroxide ion in water
-1
Hydroxide Ion
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 (ammonia) is a base even though it doesn’t
contain “-OH” as the anion
Example #7
NaOH
Example #7
Sodium
NaOH
Hydroxide
Sodium Hydroxide
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