CHM 1032C Learning Tools

Acids and Bases

Nomenclature of Acids In the aqueous phase (most common), use hydro+stem+ic acid. Examples: HCl is hydrochloric acid, HBr is hydrobromic acid and HF is hydrofluoric acid. Always assume aqueous unless otherwise specified.

In the gas phase (rare), use hydrogen stem+ide gas. Examples: HCl is hydrogen chloride gas, HBr is hydrogen bromide gas, H2S is hydrogen sulfide gas.

 These acids are composed of polyatomic ions and hydrogen.

If the polyatomic ion ends in "ate", the acid name is stem+ic acid. Examples: HNO3 is nitric acid, H3PO4 is phosphoric acid and H2SO4 is sulfuric acid.

If the polyatomic ion ends in "ite", the acid name is stem+ous acid. Examples: HNO2 is nitrous acid, HClO2 is chlorous acid and H2SO3 is sulfurous acid.
 
 

 Ionization of Acids
Acid + water ® hydronium ion + anion (strong acid)
Acid + water « hydronium ion + anion (weak acid)


Strong acids ionize 100% in water: HCl, HNO3, HClO4, H2SO4

Example: HCl(g) + H2O(l) ® H3O+(aq) + Cl-(aq)

Weak acids ionize less than 100% in water. Common examples: H3PO4, CH3CO2H, H2CO3

Example 1:  CH3CO2H(aq) + H2O(l) « H3O+(aq) + CH3CO2- (aq)

Example 2: H3PO4(aq) + H2O(l) « H3O+(aq) + H 2PO4-(aq)
H 2PO4-(aq) + H2O(l) « H3O+(aq) + H PO42-(aq)
H PO42-(aq) + H2O(l) « H3O+(aq) + PO43-(aq)


Notice that polyprotic acids ionize one hydrogen at a time, and that the first ionization proceeds to a greater extent than the second ionization, etc. This is true for sulfuric acid, too.

Example: H2SO4(aq) + H2O(l) ® H3O+(aq) + H SO4-(aq) 100% ionized
H SO4-(aq) + H2O(l) « H3O+(aq) + SO42-(aq) Less than 100% ionized
 

Bases

Strong bases are water soluble metal hydroxides. As ionic compounds, they are strong electrolytes and simply disassociate 100% in water. This is not a chemical change! Common examples are the alkali metal hydroxides and the alkaline earth metal hydroxides.

Weak bases ionize water: base + water ® cations + hydroxide ions

Example: ammonia ionizes in water to produce hydroxide ions and ammonium ions

NH3(aq) + H2O(l) « NH4+(aq) + OH-(aq)
 
Last modified December 28, 1998               Top        For more information, contact:  ksanchez@fccj.org