Calculate the percent ionization of formic acid in a 0.010 M HCOOH solution.(K_a = 1.7 * 10^-4)

Question

Quizplus · Accepted Answer

The percent ionization of a weak acid is defined as:

% ionization = (concentration of ionized acid / initial concentration of acid) x 100

We can use the Ka expression for formic acid to determine the concentration of ionized acid:

Ka = [H+][HCOO-]/[HCOOH]

Since we can assume that x (the concentration of H+) is small compared to the initial concentration of formic acid, we can simplify the expression to:

Ka = x^2 / 0.010

Solving for x, we get:

x = sqrt(Ka x 0.010) = sqrt(1.7x10^-4 x 0.010) = 1.3x10^-3 M

Therefore, the concentration of ionized formic acid is 1.3x10^-3 M. The initial concentration of formic acid is 0.010 M.

% ionization = (1.3x10^-3 / 0.010) x 100 ≈ 13%

Therefore, the answer is choice B.

Calculate the Percent Ionization of Formic Acid in a 0