Question

Which among the following acts as a basic buffer solution? (a) \(\mathrm{NH}_{4} \mathrm{Cl}+\mathrm{NH}_{4} \mathrm{OH}\) (b) \(\mathrm{NaCl}+\mathrm{NaOH}\) (c) \(\mathrm{NH}_{4} \mathrm{Cl}+\mathrm{CH}_{3} \mathrm{COOH}\) (d) \(\mathrm{CH}_{3} \mathrm{COONa}+\mathrm{CH}_{3} \mathrm{COOH}\)

Short answer

(a) NH_4Cl+NH_4OH is the basic buffer solution.

Step-by-step solution

Understanding buffer solutions

A buffer solution resists changes in pH when small amounts of acid or base are added. There are two main types of buffer solutions: acidic and basic. A basic buffer solution consists of a weak base and its salt.

Analyze each option

Examine each set of components: (a) Ammonium chloride (NH_4Cl) and ammonium hydroxide (NH_4OH): Ammonium hydroxide is a weak base, and ammonium chloride is its salt. (b) Sodium chloride (NaCl) and sodium hydroxide (NaOH): Sodium hydroxide is a strong base, not typically used in buffer solutions with NaCl. (c) Ammonium chloride (NH_4Cl) and acetic acid (CH_3COOH): Involves a weak acid rather than a weak base and its salt. (d) Sodium acetate (CH_3COONa) and acetic acid (CH_3COOH): This is an acidic buffer, as it involves a weak acid (acetic acid) and its salt (sodium acetate).

Identify the correct basic buffer

From the previous analysis, option (a) NH_4Cl+NH_4OH is the correct basic buffer. It consists of the weak base ammonium hydroxide and its salt ammonium chloride.

Key concepts

Understanding Basic Buffers

Basic buffer solutions are a type of buffer solution designed to resist changes in pH upon the addition of small amounts of acid or base. They typically consist of a weak base and its related salt, which work together to maintain a stable pH level. This happens because the weak base neutralizes any added acid, while the salt takes care of any added base.

Having a buffer solution is like setting up a protective barrier against sudden pH swings, which can disrupt chemical processes. In a basic buffer, the presence of a weak base means it doesn’t completely dissociate in water, helping to moderate the pH within a specific range. This quality of basic buffers is essential in various chemical and biological applications where pH stability is crucial.

For example, systems like the human blood rely on buffers to maintain a pH that is compatible with vital biological functions. Without these buffers, essential reactions in our bodies could be compromised.

The Role of Weak Bases

Weak bases are fundamental to creating basic buffers, which don't fully ionize in water. Because they only partially dissociate, they allow for the buffer solution to stabilize the pH when acids are introduced. Weak bases achieve this by binding to the excess hydrogen ions (\( H^+ \)), thus reducing the acidity of the solution.

One should remember that if the base were strong, the buffer solution wouldn't work. Strong bases dissociate completely in water and don’t provide the balance needed to moderate pH changes effectively. This partial dissociation inherent in weak bases is what gives basic buffers their desirable buffering capacity. Additionally, the salt of the weak base helps in neutralizing any added hydroxide ions (\( OH^- \)), ensuring the pH does not swing entirely toward basicity.

Hence, identifying whether a chemical is a weak base can decide its effectiveness in forming a buffer solution. It makes comparing options like sodium hydroxide and ammonium hydroxide much clearer, where the latter would be preferable in a buffer context due to its weak base properties.

Ammonium Chloride and Ammonium Hydroxide Pairing

One of the classic examples of a basic buffer solution is the combination of ammonium chloride (\( NH_4Cl \)) and ammonium hydroxide (\( NH_4OH \)). This pair is particularly effective because ammonium hydroxide acts as the weak base, while ammonium chloride serves as its salt. Together, they form an excellent basic buffer system.

The ammonium hydroxide in this pair provides the system's key weak base attribute, as it only partially dissociates in water. When an acid is added to the solution, the ammonium ions (\( NH_4^+ \)) from ammonium chloride combine with the hydrogen ions (\( H^+ \)), thus neutralizing the acid's effect and maintaining the pH level.

By understanding this pairing, it's easier to see why option (a) in the original exercise stands out as the correct answer for a basic buffer. It perfectly exemplifies the synergy between a weak base and its corresponding salt in keeping the pH consistent, making it a reliable choice for buffering applications in various scientific fields.