Solution: Butyric acid is responsible for the foul smell of rancid butter. The pKa of butyric acid is 4.84.Calculate the pKb for the butyrate ion.

Problem

Butyric acid is responsible for the foul smell of rancid butter. The pKa of butyric acid is 4.84.

Calculate the pKb for the butyrate ion.

Solution

We are asked to determine the pKb of the butyrate ion given the pKa of butyric acid.

Butyric acid is a weak acid (i.e. does not completely dissociate in solution). 

The dissociation in water is:

C4H8O2(aq) + H2O(l)→C4H7O2-(aq) + H3O+(aq) pKa = 4.84.

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