Mechanism of Buffering Action

The ability of a solution to withstand changes in pH when a tiny amount of acidic solution or base is added is termed a buffer action. A buffer is a solution containing an equal quantity of weak acid and conjugate base. A buffer solution composed of CH3COOH with CH3COONa can be used to demonstrate how a buffer solution works. Equivalent molar quantities of sodium ethanoate and ethanoic acid can be mixed in water to make a buffer solution. The circumstance in the solution is as follows:

CH3COOH (aq) ↔ CH3COO– (aq) + H+ (aq)

CH3COONa (aq) → CH3COO– (aq) + Na+ (aq)

An acidic buffer composed of an acidic solution like Acetic acid and its sodium salt, Sodium acetate, could explain the process of buffer action. However, sodium acetate occurs as both acetate and Na+ ions.

Mechanism

The salt is entirely made up of ions. As a result, the buffer comprises both acid (CH3COOH) and the conjugate base (CH3COO–). Whenever a tiny amount of just an acid is introduced, its conjugate base (CH3COO–) removes the hydrogen ions accordingly:

H+ (aq) + CH3COO– (aq) ↔ CH3COOH (aq)

The pH of the resultant solution will stay almost constant because ethanoic acid is very weakly decomposed, and in the state CH3COOH, it doesn’t add any H+ ion. There is no discernible drop in pH due to eliminating the majority of the injected H+. Since CH3COOH is a weak acid, its ions tend to produce non-ionised CH3COOH molecules; the process is practically complete. When a strong base is introduced, the extra OH– ion is neutralised by the interaction with acid inside the buffer.

CH3COOH (aq) + OH– (aq) → CH3COO– (aq) + H2O (l)

It’s also possible to imagine that the extra OH- ion combines with the H+ ion and forms water. The introduced OH- ions are withdrawn, and the acid equilibrium moves towards the right to compensate for the H+ ions that were used up. As a result, the pH value changes only slightly. When a droplet of NaOH is added, the OH- ions combine with free acid, resulting in water molecules.

The pH stays constant because more OH- ions of the base are absorbed or neutralised. Such resistance towards alteration in pH on the introduction of the base is described as reserve acidity and therefore is related to CH3COOH. The outcome is that CH3COOH neutralises most of the supplied OH– ions. As a result, there is no discernible variation in pH. Whenever a strong base is supplied, the acid contained inside the buffer neutralises the hydroxide ions (OH-) 

The impact of the other acids and bases is successfully balanced in either situation, ensuring that ph stays relatively constant. The mechanism of virtual buffers may be explained in the same way. Thus, the weak acid & weak base persist in the solution at large concentrations as they only infrequently interact with water. Nevertheless, they are likely to respond with any extra strong basic or strong acid.

Characteristics of a Buffer

A buffer resists pH changes by containing a reasonably high concentration of the acid or base, or, more commonly, both.

• Has a certain pH level.
• The pH value doesn’t alter after a lengthy period of storage.
• Dilution does not affect the pH of the solution.
• The pH value remains unchanged even when a modest amount of such a strong acid or base is added.

Conclusion

A buffer seems to be a liquid made up of an acidic solution and its salt or perhaps a weak base or its salt (base buffer). When a tiny quantity of acids or bases is given to it, its pH varies very little, and it is therefore employed to keep a solution’s pH stable. 

Buffer solutions are utilised in a variety of chemical processes. In reality, a buffer solution may be found in the form of blood. The pH of human blood is 7.4 in its normal state. Several individuals experience severe stress as well as alkalosis. Alkalosis is indeed a condition wherein the blood pH is abnormally high. Acidosis is just a condition in which the level in the blood is higher than 7.4. Certain chemical reactions can only take place at a specific pH. Other home and commercial goods, like shampoo, must check the pH values to battle the soap’s alkalinity to prevent irritation, baby lotion must maintain a pH of approximately 6 to prevent bacterial proliferation, laundry detergent, eye drops, carbonated lemonade, etc.