Acid and base theories: Arrhenius, Brønsted-Lowry, Lewis

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Acid and Bases -- SL

The Three Theories of Acids and Bases

1. Arrhenius Theory

States that

Acids are substances which produce hydrogen ions in solution

Bases are substances which produce hydroxide ions in solution

2. Bronsted Lowry Theory

States that

Acids are proton donors

Bases are proton acceptors

Also that, members of a conjugate pair differ from each other by the presence or absence of the transferable hydrogen ion.

3. The Lewis Theory

States that

An acid is an electron pair acceptor (acid accepts)

A base is an electron pair donor

Acid Strength

A strong acid is one which is virtually 100% ionized in solution

completely ionizes

is thus a strong electrolyte

However, the conjugate base is weaker as it has a negligible tendency to be protonated

Examples: sulfuric acid, (H2SO4) nitric acid (HNO3)

As acid strength decreases, conjugate base strength increases.

Weak acids: Acetic acid, carbonic acid, any carboxylic acid

Base Strength

strong base ionizes completely in solution

completely ionizes

is a strong electrolytes

Examples: Sodium hydroxide (NaOH), Potassium Hydroxide (KOH), Barium hydroxide(Ba(OH)2)

Weak bases: Methylamine, ammonia, any amine

Identifying strong acids

Reaction

with carbonates faster

effervescence

Reaction

with metals faster

effervescence

Electrical

conductivity better

conductor

pH lower

Temperature

changes more exothermic

Identifying strong bases

Reaction

with acids faster rate

Electrical

conductivity better

conductor

pH higher

Temperature

changes more exothermic

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