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Horvath Practice Problems 52

# Horvath Practice Problems 52 - the equilibrium expression...

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13 ACID AND BASE EQUILIBRIA Up until now we have been considering strong acids and bases in which the acid or base fully dissociates. For weak acids and bases we must set-up an equilibrium ex- pression. For a weak acid equilibrium reaction, HA ­ H + + A , (13.1) the equilibrium expression is K a = £ H + ¤ £ A ¤ [ HA ] (13.2) where K a is called the acid dissociation constant. The larger the K a the stronger the acid Likewise for a weak base equilibrium reaction, BOH ­ B + + OH , (13.3)
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Unformatted text preview: the equilibrium expression is K b = £ OH − ¤£ B + ¤ [ BOH ] (13.4) where K b is called the base dissociation constant. There is a relationship between K a and K b for conjugate acid— base pairs. The relationship is K a K b = K w . (13.5) If the acid (or base) is polyprotic then there are multiple K a values ( K a 1 , K a 2 , etc.) for each of the dissociation reactions. ACID AND BASE EQUILIBRIA 51...
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