You would like to make a 100 mL buffer solution at pH 8.00. Assuming you would like to accomplish this with a hypochlorous acid (HOCl) buffer (HOCl/NaOCl), Ka= 3.0 * 10-8. If the solution is 0.3 M in HOCl, what concentration of NaOCl would be necessary in the buffer solution to obtain a pH of 8.0?

To obtain the pH of 8.0, the concentration of NaOCl needs to be 0.9 M in the 0.3 M HOCl solution

Explanation:

This problem can be solved by Henderson-Hasselbalch equation, which gives relation between the concentration of acid, its salt, pKa and the pH of the solution. This equation is given as,

By placing the known variables in the above equation we get,

The above calculations show that the required concentration of NaOCl is 0.9 M.

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