The K_a of hypobromous acid,HOBr,is 2.6 × 10−⁹.Calculate the pH of a solution which is composed of 0.40 M HOBr and 0.40 M NaOBr.

Question

Quizplus · Accepted Answer

The solution is a buffer solution composed of a weak acid (HOBr) and its conjugate base (OBr-). The pH of such a solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base and [HA] is the concentration of the acid. Given that the Ka of HOBr is 2.6 × 10^-9, the pKa is -log(2.6 × 10^-9) ≈ 8.59. Since the concentrations of the acid and its conjugate base are equal, the log([A-]/[HA]) term equals log(1) = 0. Therefore, the pH of the solution is approximately equal to the pKa, which is 8.59.

The Ka of Hypobromous Acid,HOBr,is 2

The K_a of Hypobromous Acid,HOBr,is 2