Question

Enough of a monoprotic acid is dissolved in water to produce a 1.211.21 M solution. The pH of the resulting solution is 2.882.88 . Calculate the Ka for the acid.

Answer 1

Answer:

1.44 × 10⁻⁶

Explanation:

Step 1: Given data

• Concentration of the acid (Ca): 1.21 M

• pH of the solution: 2.88

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