Explain why a mixture of \(\mathrm{CH}_{3} \mathrm{COOH}\) and \(\mathrm{CH}_{3} \mathrm{COONa}\) can act as a buffer while a mixture of \(\mathrm{HCl}\) and \(\mathrm{NaCl}\) cannot.

A buffer solution is a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid. Buffer solutions resist a change in pH when small amounts of an acid or base are added to them. The capacity of a buffer solution to resist pH changes depends on the presence of both the weak acid/base and its corresponding conjugate base/acid in equilibrium. Buffer solutions can be made from two components: 1. A weak acid (HA) and its conjugate base (A-) in a solution 2. A weak base (B) and its conjugate acid (HB+) in a solution The ability of a buffer solution to resist pH changes depends on two factors: 1. The concentration ratio of weak acid/base to its conjugate base/acid 2. The acid dissociation constant (Ka) of the weak acid/base

The mixture of CH3COOH (acetic acid) and CH3COONa (sodium acetate) contains a weak acid and its conjugate base. Acetic acid is a weak acid that partially ionizes in water, forming the acetate anion (CH3COO-) and the hydronium ion (H3O+): \[CH_3COOH \rightleftharpoons CH_3COO^{-} + H_3O^+\] Sodium acetate is a salt that dissociates completely in water, releasing the acetate anion (CH3COO-) and the sodium cation (Na+): \[CH_3COONa \rightarrow CH_3COO^{-} + Na^{+}\] In the mixture, we have both the weak acid (CH3COOH) and its conjugate base (CH3COO-). When an acid or base is added to this mixture, the weak acid and its conjugate base can react to minimize pH changes. Therefore, this mixture can act as a buffer solution.

The mixture of HCl (hydrochloric acid) and NaCl (sodium chloride) contains a strong acid instead of a weak acid or base. Hydrochloric acid is a strong acid that completely ionizes in water, forming chloride anion (Cl-) and the hydronium ion (H3O+): \[HCl \rightarrow Cl^{-} + H_3O^+\] Sodium chloride is a salt that dissociates completely in water, releasing the chloride anion (Cl-) and the sodium cation (Na+): \[NaCl \rightarrow Cl^{-} + Na^{+}\] In the mixture, we have a strong acid (HCl) and its conjugate base (Cl-), which is a very weak base. However, the strong acid does not have the ability to resist pH changes when small amounts of an acid or base are added. Consequently, this mixture cannot act as a buffer solution.

A mixture of CH3COOH (acetic acid) and CH3COONa (sodium acetate) can act as a buffer solution because it contains a weak acid and its conjugate base. This mixture can resist pH changes when small amounts of an acid or base are added. On the other hand, a mixture of HCl (hydrochloric acid) and NaCl (sodium chloride) cannot act as a buffer solution because it contains a strong acid and its conjugate base, which do not have the ability to resist pH changes.