Part A Pyridine is a weak base that is used in the manufacture of pesticides and

Question

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(aq)+H2O(l)C5H5NH+(aq)+OH(aq)

The pKb of pyridine is 8.75. What is the pH of a 0.360 mol L1 solution of pyridine?

Express the pH numerically to two decimal places.

View Available Hint(s)

Submit

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:

C6H5COOH(aq)+H2O(l)C6H5COO(aq)+H3O(aq)

The pKa of this reaction is 4.2. In a 0.63 mol L1 solution of benzoic acid, what percentage of the molecules are ionized?

Express your answer to two significant figures and include the appropriate units.

View Available Hint(s)

Explanation / Answer

part A

pH of weak base = 14 - (1/2(pkb-logC))

pkb = - logkb = 8.75

C = concentration of pyriidne = 0.36 M

pH = 14 - (1/2(8.75-log0.36)) = 9.40

part B

pka = - logka

4.2 = -logka

Ka = 6.31*10^-5

Ka = CX^2

(6.31*10^-5) = 0.63*x^2

x = 0.01 = degree of dissociation

percentage of dissociation = x*100

                           = 0.01*100

           = 1.0 %

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.