Answer:
1.44 × 10⁻⁶
Explanation:
Step 1: Given data
Step 2: Calculate the concentration of H⁺ ions
We will use the definition of pH.
pH = -log [H⁺]
[H⁺] = antilog -pH = antilog -2.88 = 1.32 × 10⁻³ M
Step 3: Calculate the acid dissociation constant of the acid (Ka)
For a weak monoprotic acid, we will use the following expression.
Ka = [H⁺]²/Ca
Ka = (1.32 × 10⁻³)²/1.21 = 1.44 × 10⁻⁶