Pyridine is a weak base that is used in the manufacture of pesticides and plasti
ID: 504911 • Letter: P
Question
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: C_5H_5N + H_2O C_5H_5NH^+ + OH^- The pK_b of pyridine is 8.75. What is the pH of a 0.260 M solution of pyridine? (Assume that the temperature is 25 degree C.) 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 ionizes in water. C_6H_5COOH C_6H_5COO^- + H^+ The pK_a of this reaction is 4.2. In a 0.58 M solution of benzoic acid, what percentage of the molecules are ionized?Explanation / Answer
pKb = 8.75
Kb = 1.78 x 10^-9
C5H5N + H2O ------------------> C5H5NH+ + OH-
0.260 0 0
0.260 - x x x
Kb = x^2 / 0.260 - x
1.78 x 10^-9 = x^2 / 0.260 - x
x = 2.15 x 10^-5
[OH-] = 2.15 x 10^-5 M
pOH = -log (2.15 x 10^-5 ) = 4.67
pH = 9.33
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.