Acids and Bases. Experimental Definitions

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Acids and Bases: Experimental Definitions

Acids:

taste sour

turn litmus red

react with active metals to release hydrogen gas

react with bases to form water and a salt

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Acids and Bases: Experimental Definitions

Bases:

taste bitter

turn litmus blue

feel slippery

react with acids to form water and a salt

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Acids and Bases

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Acids, Bases, and Salts

Arrhenius Theory

Acid: a molecular substance that ionizes in aqueous solution to form hydrogen ions (H+)

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Acids, Bases, and Salts

Arrhenius Theory

Base: a substance that produces hydroxide ions (OH-) in aqueous solution

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Acids, Bases, and Salts

Neutralization: When an acid reacts with a base, the properties of each are neutralized and the products are water and a salt.

Acid + Base --> Water + Salt

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Acids, Bases, and Salts

Limitations of the Arrhenius Theory

- H+ ions do not exist in water solution. Protons react with water to form hydronium ions. (H3O+)

H+ + H2O --> H3O+

The Arrhenius Theory does not explain the basicity of ammonia and similar compounds.

It only applies to reactions in aqueous solution.

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Acids, Bases, and Salts

Brønsted-Lowry Theory

Acid: proton donor

HA + H2O --> H3O+ + A-

Base: proton acceptor

NH3 + H2O --> NH4+ + OH-

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Nonmetal oxides are acidic

SO3 + H2O --> H2SO4

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Metal oxides are basic.

Example:

Lime (calcium oxide) reacts with water to form slaked lime (calcium hydroxide).

CaO + H2O --> Ca(OH)2

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Strong and Weak Acids and Bases

Strong acids ionize completely in water solution. 100%

HCl(aq) --> H+(aq) + Cl-(aq)

Weak acids only partially ionize in water solution.

HCN(aq) --> H+(aq) + CN-(aq)

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