An unknown weak acid with a concentration of 0.440 M has a pH of 5.600. What is the Ka of the weak acid?

1.43 × 10⁻¹¹

Explanation:

Step 1: Given data

Step 2: Calculate the concentration of H⁺

We will use the definition of pH.

pH = -log [H⁺]

[H⁺] = antilog -pH = antilog -5.600 = 2.512 × 10⁻⁶ M

Step 3: Calculate the acid dissociation constant (Ka)

For a weak acid, we can calculate Ka using the following expression.

Ka = [H⁺]²/Ca

Ka = (2.512 × 10⁻⁶)²/0.440 = 1.43 × 10⁻¹¹