Naming Acids
Dr. Jerry E. Sipe
Ivy Tech Community College
What You Need To Know
• Acid nomenclature is different from other
compound nomenclature
• Acids are named for their anions because
they have a common cation: H+
• Other compounds are named for their
cations and their anions
Classification of Acids
• Classified by the number of hydrogen ions
produced
– Monoprotic: HCl  H+ + Cl– Diprotic: H2SO4  2 H+ + SO4-2
– Triprotic: H3PO4  3 H+ + PO4-3
– Recognizing this classification is vital when
stoichiometry/balancing equations are
required
Classification of Acids
• Classified by type of anion
– Binary: monatomic anion: HCl
– Tertiary: polyatomic anion: H2SO4
– Recognizing this classification is vital in
naming acids and writing formulas from
their names
Writing Acid Formulas:
Binary Acids
• Formula writing begins with analyzing the key
parts of the name
• Binary acids are recognized by the following:
• HYDROELEMENTIC
H+
E-X
CROSS MULTIPLY CHARGES
HX E
Hydrochloric Acid
Indicates a binary acid containing chlorine
+
H
Cl
HCl
1
1
Writing Acid Formulas:Tertiary
Acids – Names ending in “ous”
• POLYATOMICSTEMOUS ACID
H+
ZO-X
CROSS MULTIPLY CHARGES
HXZO
Nitrous Acid
Indicates a polyatomic anion with lowest
amount of oxygen in nitrogen series (nitrite)
NO2
+
H
H NO
1
21
-
Writing Acid Formulas:Tertiary
Acids – Names ending in “IC”
• POLYATOMICSTEMIC ACID
H+
ZO2
-X
CROSS MULTIPLY CHARGES
HXZO2
Sulfuric Acid
Indicates a polyatomic anion with highest
amount of oxygen in sulfur series
SO4
+
H
H2SO4 1
-2
Perchloric acid
Indicates a polyatomic anion with highest
amount of oxygen in chlorine series
ClO4
+
H
H1ClO4 1
-
Hydrophosphoric Acid
Indicates a binary acid containing
phosphorous
+
H
-3
P
H3P1
Hydroiodic Acid
Indicates a binary acid containing iodine
+
H
I
H1I1
Hypochlorous Acid
Indicates a polyatomic ion with the lowest
level of oxygen in the chlorine series
+
H
ClO
HClO
1
1
Naming of Acids:
Formula to Name
• Acid names derived from the anion
• Binary acids: HYDROELEMENTIC ACID
• Example: HI  IODIDE ion is anion
• Therefore the name of the acid is
– HYDROIODIC ACID
Naming of Acids:
Formula to Name
• Tertiary acids “ite” ending: ITE  OUS
– ION NAME STEMOUS ACID
– Example: HPO3; PO3-3 is the phosphite ion;
therefore, the name of the acid is
PHOSPHOROUS ACID
– Note: the “OR” in the name is added to complete
the elemental name
Naming of Acids:
Formula to Name
• Tertiary acids “ic” ending: ATE  IC
– ION NAME STEMIC ACID
– Example: HPO4; PO4- is phosphate ion; therefore,
the name of the acid is PHOSPHORIC ACID
– Note: the “OR” in the name is added to complete
the elemental name
H2 S
Only one element (sulfur) other than
hydrogen – a binary acid; therefore…
Hydrosulfuric Acid
H2SO3
Sulf ite Ion
Sulfurous Acid
HNO3
Nitrate Ion
Nitric Acid
HF
Only one element (fluorine) other than
hydrogen – a binary acid; therefore…
Hydrofluoric Acid
HClO3
Chlorate Ion
Chloric Acid
HIO
Hypoiodite Ion
Hypoiodous Acid