The pKa of hypochlorous acid
The pKa of hypochlorous acid is 7.530. A 52.0 ml solution of 0.149 M sodium hypochlorite (NaOCl) is titrated with 0.293 M HCl. Calculate the pH of the solution.
What is the pH of the solution in the titration experiment?
The pH of the buffer solution is 7.236
Explanation:
Henderson - Hasselbalch equation of a buffer solution consisting of a weak acid and its conjugate base is given as:
pH=pKa+log([conjugate base]/[weak acid])
The hypochlorous acid (HClO) is the weak acid and the conjugate base the hypochlorite anion (ClO⁻) is the conjugate base.
The dissociation of the salt is given by:
NaOCl(aq) ⇒ Na⁺(aq) + ClO⁻(aq)
The salt dissociates at a ratio of 1:1
Substituting values to get:
pH=pKa+log([conjugate base]/[weak acid])
pH=7.53+log(0.149M/0.293M)
pH=7.53-0.2937
pH=7.236
The pH of the buffer solution is 7.236