Question

An aqueous solution contains 0.30 M hypochlorous acid. One Liter of this solution could be converted into a buffer by the addition of: (Assume that the volume remains constant as each substance is added.) 0.31 mol KClO 0.30 mol KBr 0.15 mol HCl 0.074 mol Ca(OH)2 0.31 mol HCl

Answer 1

As a solution, 0.31 mol of KClO can be added to one liter of 0.3 M HClO to provide a buffer solution.

Step-by-step explanation:

A buffer system is made up of a weak acid, a base and its corresponding salt. The pH of the buffer can be calculated using the Henderson-Hasselbach equation, which is the same

pH = pKa + log ([Salt] / [Acid]).

In the example, a hypochlorous acid buffer should have the hypochlorous acid salt, which may be potassium hypochlorite. Potassium perchlorate is not a buffer, because the perchloric acid ion is missing.

Furthermore, nitric acid and sodium hydroxide are a strong acid and a strong base. So they are not able to partially ionize, which is required for a buffer. This partial ionization is important, because it is what makes the buffer maintain the pH of the solution in the addition of the acid or base. Strong acids and bases do not serve as a buffer.

Answer 2

Step-by-step explanation:

Every buffer system comprises of a weak acid or a base and its salt. The pH of the resultant buffer is calculated by the Henderson-Hassel Bach equation as pH = pKa + log ([Salt]/[Acid]). Thus, a hypochlorous acid buffer should also contain a salt of hypochlorous acid, which among given is potassium hypochlorite (KClO). Potassium perchlorate on the other hand does not function as a buffer, as the counter ion by perchloric acid is not present, preventing common ion effect from arising for the perchlorate anion.

Nitric acid and sodium hydroxide are strong acid and base. Hence, they will not undergo partial ionization required for equilibrium adjustment necessary in a buffer. In a buffer, the partial ionization of the parent acid or base is essential as it is that factor that helps the buffer maintain pH during acid or base addition by simply increasing or decreasing the parent acid/base's ionization depending upon the excess quantity of proton of hydroxyl ions present. Such a reversible dissociation however is not possible in strong acids and bases rendering them useless as buffer components.

Therefore, among the given chemicals, 0.31mol KClO can be added to a liter of 0.3M HClO to afford a buffer.