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

step 1 So starting with PkA value multiplied with PKB value will give me equilibrium constant PKB, PKW

Butyric acid is responsible for the foul smell of rancid...

Butyric acid is responsible for the foul smell of rancid butter. The $\mathrm{pK}_{a}$ of butyric acid is 4.84 (a) Calculate the pK $_{b}$ for the butyrate ion. (b) Calculate the pH of a 0.050 $M$ solution of butyric acid. (c) Calculate the pH of a 0.050$M$ solution of sodium butyrate.

Key Concepts

pKa and pKb Relationship

This concept revolves around the intrinsic relationship between an acid and its conjugate base in aqueous solution. The pKa value measures the strength of an acid, while the pKb value measures the strength of its conjugate base. In water at 25 °C, these values are related by the equation pKa + pKb ? 14, which allows calculation of one value if the other is known.

Weak Acid Equilibrium

In a solution of a weak acid, the acid partially dissociates into its conjugate base and hydrogen ions, establishing an equilibrium described by its acid dissociation constant (Ka). Analyzing this equilibrium typically involves setting up an ICE table to quantify the concentrations of all species at equilibrium, which in turn enables calculation of the pH of the solution.

Conjugate Base Hydrolysis

When a salt containing the conjugate base of a weak acid is dissolved in water, the conjugate base can react with water in a process called hydrolysis. This reaction produces the weak acid and hydroxide ions, thereby increasing the pH of the solution. Calculations often use the base dissociation constant (Kb), which can be derived from the pKa of the corresponding weak acid using the relationship pKa + pKb = 14.

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