Answer:
5.7 × 10⁻³ M
Explanation:
Step 1: Given and required data
pH of the solution: 3.5
Ka of acetic acid: 1.8 × 10⁻⁵
Step 2: Calculate the concentration of H⁺
pH = -log [H⁺]
[H⁺] = antilog -pH = antilog -3.5 = 3.2 × 10⁻⁴
Step 3: Calculate the initial molar concentration of acetic acid (Ca)
Acetic acid is a weak acid. We can calculate its initial concentration using the following expression.
Ca = [H⁺]²/Ka
Ca = (3.2 × 10⁻⁴)²/1.8 × 10⁻⁵
Ca = 5.7 × 10⁻³ M
