Properties of Acids and Bases
Acids and bases have characteristics different from most other materials. The following table gives properties and examples of each:
Property
Taste Touch Reactivity with metals Conducts electricity? pH Reaction with phenolphthalien indicator Reaction with universal indicator Examples |
Acid
Tart Will sting, especially on a cut Vigorously and produces bubbles Yes 0 to below 7 Colorless Red, orange, yellow Fruits, soft drinks, coffee, milk |
Base
Bitter Feels slippery, because it is dissolving skin No reaction Yes above 7 to 14 Pinkish-purple Blue, violet Blood, eggs, soap, ammonia, drain cleaner |
Definitions of Acids and Bases
There are two definitions for the classification of acids and bases. The first is called the Arrhenius Definition (1884). Arrhenius said that acids and bases release specific ions in water:
There are two definitions for the classification of acids and bases. The first is called the Arrhenius Definition (1884). Arrhenius said that acids and bases release specific ions in water:
Acids - dissociate to produce H+ ions in water
Bases - dissociate to produce OH- (hydroxide) ions in water
Or in simpler terms, a substance that begins with H+ will be an acid. like HCl (stomach acid) and H2SO4 (battery acid). A substance that ends with an OH- will be a base, like NaOH and Ca(OH)2 (drain cleaners).
Bases - dissociate to produce OH- (hydroxide) ions in water
Or in simpler terms, a substance that begins with H+ will be an acid. like HCl (stomach acid) and H2SO4 (battery acid). A substance that ends with an OH- will be a base, like NaOH and Ca(OH)2 (drain cleaners).
This definition will help to identify many acids and bases. However, there are several materials that have acidic and basic properties which do not fit in this definition, so another, more complete definition was designed. This more complete definition is called the Bronsted-Lowery Definition (1923)
Bronsted and Lowery independently said that acids and bases can be thought of H+ donors and acceptors:
Acids donate H+ ions
Bases accept H+ ions
Acids donate H+ ions
Bases accept H+ ions
For example, when nitrogen trihydride is placed in water, it undergoes this reaction:
NH3 (g) + H2O (l) --> NH4+ (aq) + OH- (aq)
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