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Ch.15 - Acid and Base EquilibriumWorksheetSee all chapters

# Polyprotic Acid

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Sections
Identifying Acids and Bases
Arrhenius Acid and Base
Bronsted Lowry Acid and Base
Amphoteric
Lewis Acid and Base
pH and pOH
Ka and Kb
Ionic Salts
Diprotic Acid
Polyprotic Acid

polyprotic acid possesses more than 2 hydronium ions (H+).

###### Polyprotic Acids

Our understanding of diprotic acids and bases can be used to understand polyprotic acids and bases.

Concept #1: The most common type of polyprotic acid is the triprotic acid, which contains 3 acidic hydronium ions.

Concept #2: Triprotic bases contain 3 Kb values, so they would have 3 equilibrium equations.

Concept #3: As a result of these equations for polyprotic acids and bases the relationship between Ka and Kb can be established.

Example #1: Determine the pH of 0.300 M sodium hydrogen phosphate, Na2HPO4. Phosphoric acid, H3PO4, contains Ka1 = 7.5 x 10-3, Ka2 = 6.2 x 10-8 and Ka3 = 4.2 x 10-13

Example #2: Determine the pH of 0.300 M citric acid, H3C6H5O7 it possesses Ka1 = 7.4 x 10-4, Ka2 = 1.7 x 10-5 and Ka3 = 4.0 x 10-7