Para-Aminobenzoic acid (PABA),p-H₂NC₆H₄(COOH),is used in some sunscreens and hair conditioning products.Calculate the pH of an aqueous solution with [PABA] = 0.030 M and K_a = 2.2 × 10^-5.

Question

Quizplus · Accepted Answer

PABA is a weak acid, and its dissociation in water can be represented as HA ⇌ H+ + A-. The pH of the solution can be calculated using the formula pH = 1/2(pKa - log[HA]), where pKa = -log(Ka). Given Ka = 2.2 × 10^-5, pKa = -log(2.2 × 10^-5) ≈ 4.66. Substituting the values, pH = 1/2(4.66 - log(0.030)) ≈ 3.09.

Para-Aminobenzoic Acid (PABA),p-H2NC6H4(COOH),is Used in Some Sunscreens and Hair Conditioning

Para-Aminobenzoic Acid (PABA),p-H₂NC₆H₄(COOH),is Used in Some Sunscreens and Hair Conditioning