Calculate the analytical concentration of a solution of acetic acid that has a pH of 3.00 ( K _a for acetic acid is 1.8×10^{- 5}).

Question

Quizplus · Accepted Answer

The pH of a solution is defined as the negative logarithm of the hydrogen ion concentration. Therefore, we can use this formula to calculate the hydrogen ion concentration:
pH = -log[H+]
Rearranging the formula, we get:
[H+] = 10-pH
Substituting the given pH of 3.00, we get:
[H+] = 10-3.00 = 1.00 × 10-3
Since acetic acid is a weak acid, we can use the formula for its acid dissociation constant (Ka) to calculate its concentration:
Ka = [H+][CH3COO-]/[CH3COOH]
Rearranging the formula, we get:
[CH3COOH] = [H+][CH3COOH]/Ka
Substituting the calculated [H+] and the given Ka of 1.8 × 10-5, we get:
[CH3COOH] = (1.00 × 10-3)(1.00 × 10-3)/1.8 × 10-5 = 0.056
Therefore, the analytical concentration of the acetic acid solution is 0.056 M, and the correct answer is C.

Calculate the Analytical Concentration of a Solution of Acetic Acid