Answer:
(C) HClO, pKa = 7.54
Explanation:
A buffer is a solution that can resist abrupt changes in pH when acids or bases are added. It is formed by two components:
- A weak acid and its conjugate base.
- A weak base and its conjugate acid.
In this case, acid and base are defined according to Bronsted-Löwry theory, which states that acids are substances that <em>release H⁺</em> and bases are substances that <em>accept H⁺. </em>Therefore, when an acid loses an H⁺ transforms into its conjugated base. For example, HF/F⁻ is a conjugate acid-base pair.
In buffers, when an acid is added, it reacts with the base to diminish its amount:
F⁻ + H⁺ ⇄ HF
Also in buffers, when a base is added, it reacts with the acid to diminish its amount:
HF + OH⁻ = F⁻ + H₂O
The optimum pH range of work of a buffer system (known as buffer range) is between 1 unit less and 1 unit more of pH than its pKa.
So, the buffer formed by HClO/ClO⁻ works optimally in the pH range 6.54-8.54. Since pH = 8.10 is in that interval, this would be the optimal choice.
