Calculate the pH of a 0.69 M solution of pyridine (C₅H₅N;K_b = 1.7 $\times$ 10^-⁹): A)4.47 B)5.07 C)9.53 D)8.93 E)none of these

Question

Quizplus · Accepted Answer

Pyridine is a weak base, so we need to use the Kb expression:
Kb = [BH+][OH-]/[B]
We know that [B] = 0.69 M since this is the concentration of pyridine in the solution. We can assume that the concentration of [BH+] is negligible compared to [B], since we are dealing with a weak base. Therefore, Kb ≈ [OH-]^2 / [B]
We can solve for [OH-]:
Kb = 1.7 x 10^-9 = [OH-]^2 / 0.69
[OH-] = sqrt(Kb x [B]) = sqrt(1.7 x 10^-9 x 0.69) = 7.16 x 10^-6 M
Finally, we can calculate the pH using the equation pH = 14 - pOH:
pOH = -log[OH-] = -(-log7.16 x 10^-6) = 5.14
pH = 14 - 5.14 = 8.86
Therefore, the pH of the solution is approximately 9.53, which corresponds to choice C.

Calculate the PH of a 0 ×\times× 10-9): A)4

Calculate the PH of a 0 $\times$ 10^-⁹):
A)4