Question

What two components make up a buffered solution? Give an example of a combination that would serve as a buffered solution.

Short answer

A buffered solution contains a weak acid and its conjugate base or a weak base and its conjugate acid. These components help maintain a constant pH by neutralizing added acids or bases. An example of a buffered solution is an aqueous solution containing acetic acid (CH₃COOH) and its conjugate base, the acetate ion (CH₃COO⁻). This combination can neutralize added H⁺ and OH⁻ ions, maintaining a constant pH.

Step-by-step solution

Identify the components of a buffered solution

A buffered solution contains a weak acid and its conjugate base or a weak base and its conjugate acid. Conjugate acid-base pairs help in maintaining a constant pH because the weak acid can neutralize added base while the conjugate base can neutralize added acid.

Provide an example of a buffered solution

A common example of a buffered solution is an aqueous solution containing both acetic acid (CH₃COOH) and its conjugate base, the acetate ion (CH₃COO⁻). When a small amount of acid or base is added to this solution, the following processes occur: 1. If an acid is added, some of the added H⁺ ions are consumed by the acetate ions (CH₃COO⁻) in the solution, forming acetic acid (CH₃COOH). 2. If a base is added, some of the added OH⁻ ions react with the acetic acid (CH₃COOH) in the solution to form water (H₂O) and acetate ions (CH₃COO⁻). These reactions help to maintain a constant pH in the solution, thus making it a buffered solution.

Key concepts

Weak Acid

A weak acid is an acid that only partially dissociates in solution. This means that not all of the acid molecules break apart to form hydrogen ions (H⁺) and anions. For instance, when acetic acid (CH₃COOH) is dissolved in water, only some of it dissociates into hydrogen ions and acetate ions (CH₃COO⁻).

Weak acids are important in buffer solutions because they aren't very strong. They don't release a lot of H⁺ ions at once, which makes them less drastic in changing the solution's pH. This property is precisely what allows them to interact so effectively with bases to help maintain the pH level.

In our example of a buffered solution, acetic acid acts as the weak acid. When a base is added, the acetic acid doesn’t immediately release more hydrogen ions to drastically alter the pH. Instead, it reacts slowly, maintaining balance.

Conjugate Base

A conjugate base is what remains after a weak acid has released a hydrogen ion. It is part of the acid-base pair working together to keep the pH stable. In simpler terms, it’s the partner of the weak acid in a buffer solution.

Consider the example of the acetic acid buffer. After acetic acid (CH₃COOH) donates a hydrogen ion, the resulting acetate ion (CH₃COO⁻) is the conjugate base. This conjugate base is crucial. It can capture any extra hydrogen ions that come in when acid is added, helping to neutralize them.

Imagine it as a dynamic team: the weak acid and its conjugate base. While the weak acid is protecting against too much base, the conjugate base is stepping in to tackle any excess acid. Working together, they maintain a balanced pH environment.

pH Maintenance

pH maintenance is the process of keeping the hydrogen ion concentration steady in a solution. A buffered solution excels at this because of the presence of both a weak acid and its conjugate base.

Here's how it works:

• When acid is added, the conjugate base takes charge. It captures the additional hydrogen ions, preventing a drop in pH.
• When a base is added, the weak acid steps up. It releases its hydrogen ions to neutralize the base, preventing a rise in pH.

This balanced interaction helps neutralize any sudden changes in acidity or alkalinity, maintaining the solution's pH. Simply put, buffers act like pH cushions. They absorb the blow when acid or base attempts to disrupt the solution. This makes buffered solutions essential for various applications like biological systems and laboratory experiments where pH must be kept constant.