The ionization constant, K_a, for benzoic acid, HC₇H₅O₂, is 6.28 × 10^-5. What is the pH of a 0.15 molar solution of this acid?

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Quizplus · Accepted Answer

The pH of a weak acid solution can be calculated using the formula: pH = -log[H⁺]. For benzoic acid, the concentration of H⁺ ions can be found using the expression for Kₐ: Kₐ = [H⁺][C₇H₅O₂⁻]/[HC₇H₅O₂]. Assuming x is the concentration of H⁺ ions, Kₐ = x²/(0.15 - x). Solving for x and then calculating the pH gives approximately 2.52.

The Ionization Constant, Ka, for Benzoic Acid, HC7H5O2, Is 6

The Ionization Constant, K_a, for Benzoic Acid, HC₇H₅O₂, Is 6