Unlike strong acids and bases that ionize completely in solution, weak acids or bases partially ionize. The tendency to ionize (i.e., the ionic strength) of a weak acid or base can be quantified in several ways including
Ka or Kb,
pKa or pKb,
and percent ionization.
Part A
Pyridine is a weak base that is used in the manufacture of pesticides and plastic resins. It is also a component of cigarette smoke. Pyridine ionizes in water as follows:
C5H5N+H2OâC5H5NH++OHâ
The pKb of pyridine is 8.75. What is the pH of a 0.455 M solution of pyridine?
Express the pH numerically to two decimal places.
pH=____________
Part B
Benzoic acid is a weak acid that has antimicrobial properties. Its sodium salt, sodium benzoate, is a preservative found in foods, medications, and personal hygiene products. Benzoic acid dissociates in water:
C6H5COOHâC6H5COOâ+H+
The pKa of this reaction is 4.2. In a 0.58 M solution of benzoic acid, what percentage of the molecules are ionized?
Express the percentage numerically using two significant figures.
percent ionized = _______________ %
Unlike strong acids and bases that ionize completely in solution, weak acids or bases partially ionize. The tendency to ionize (i.e., the ionic strength) of a weak acid or base can be quantified in several ways including
Ka or Kb,
pKa or pKb,
and percent ionization.
Part A
Pyridine is a weak base that is used in the manufacture of pesticides and plastic resins. It is also a component of cigarette smoke. Pyridine ionizes in water as follows:
C5H5N+H2OâC5H5NH++OHâ
The pKb of pyridine is 8.75. What is the pH of a 0.455 M solution of pyridine?
Express the pH numerically to two decimal places.
pH=____________
Part B
Benzoic acid is a weak acid that has antimicrobial properties. Its sodium salt, sodium benzoate, is a preservative found in foods, medications, and personal hygiene products. Benzoic acid dissociates in water:
C6H5COOHâC6H5COOâ+H+
The pKa of this reaction is 4.2. In a 0.58 M solution of benzoic acid, what percentage of the molecules are ionized?
Express the percentage numerically using two significant figures.
percent ionized = _______________ %