Multiple Choice
If the Kb of NH3 is 1.76 x 10-5, determine the acid dissociation constant of its conjugate acid.
4067
views
1
rank
3
comments
17. Acid and Base Equilibrium
Ka and Kb
Multiple Choice
Calculate the pH of a 0.500 M pyridine (C5H5N) solution. Kb value for pyridine is 1.7 × 10−9.
A
4.54
B
8.77
C
9.46
D
11.23
E
13.70
Verified step by step guidance1
Identify that pyridine (C5H5N) is a weak base and will partially ionize in water. The ionization can be represented by the equation: C5H5N + H2O ⇌ C5H5NH+ + OH−.
Use the base dissociation constant (Kb) expression for pyridine: Kb = [C5H5NH+][OH−] / [C5H5N]. Given Kb = 1.7 × 10^−9 and the initial concentration of pyridine is 0.500 M.
Assume that the change in concentration of pyridine due to ionization is small, so [C5H5N] ≈ 0.500 M. Let x be the concentration of OH− produced, then [C5H5NH+] = x and [OH−] = x.
Substitute the values into the Kb expression: 1.7 × 10^−9 = (x)(x) / 0.500. Solve for x to find the concentration of OH− ions.
Calculate the pOH using the formula pOH = -log[OH−]. Then, use the relationship pH + pOH = 14 to find the pH of the solution.
Related Videos
Related Practice
