A solution is prepared by adding 500 mL of 0.3 M NaClO to 500 mL of 0.4 M HClO. What is the pH of this solution? A)The pH will be greater than the pK _a of hypochlorous acid. B)The pH will be less than the pK _a of hypochlorous acid. C)The pH will be equal to the pK _a of hypochlorous acid. D)The pH will equal the pK _b of sodium hypochlorite. E)None of these choices are correct.

Question

Quizplus · Accepted Answer

When NaClO and HClO are mixed, they react to form Na+ and ClO- ions along with H2O and Cl2 gas. The reaction consumes H+ ions and thus the pH of the resulting solution will be greater than the pH of pure HClO solution. The pKa of HClO is approximately 7.5, therefore a pH of less than 7.5 would indicate that the excess HClO is adding protons and increasing the acidity of the solution. Since the pH of the resulting solution is expected to be greater than 7.5, option A and C can be eliminated. The pKb of NaClO is approximately 4.74, therefore option D can also be eliminated. Thus, the best answer is B.

A Solution Is Prepared by Adding 500 ML of 0