Answer to Question #87177 in Inorganic Chemistry for Dayo

Question

A buffer solution is made using a weak acid, HA, with a pKa of 6.40. If the ratio of A– to HA is 0.010, what is the pH of the buffer?

Answer 1

K_a = 10^-6.4.

[A^-]/[HA] = 0.01 = 10^-2.

HA ⇄ H⁺ +A^-

K_a = [H⁺][A^-]/[HA] = 10^-6.4.

[H⁺] = K_a/ ([A^-]/[HA]) = 10^-6.4/10^-2 = 10^-4.4.

pH = -log₁₀[H⁺] = -log₁₀10^-4.4 = 4.4.