Buffering Capacity

The pH of any material is crucial in the science of chemistry. One must recognise and understand the nature of the chemical, solution, or liquid. This involves understanding any chemistry-based material or solution’s acidic, basic, or neutral properties. These properties also hold significance in our daily lives. For instance, too much acidic content in food or liquid in the human body can cause injury and be deadly. This course will cover all of the fundamentals that a person needs to know about to understand the idea of buffering capacity. 

What is a Buffer?

A buffer is a solution that can withstand pH changes when acidic or basic components are added to it. It can neutralise little amounts of added acid or base, allowing the pH of the solution to remain relatively constant by absorbing partially and adding the OH- or H+ ions to the system.

There are two types of buffers, namely:

1. Acidic buffer: These include a mixture of an acid that is weak, and its salt is formed of a strong base.
2. Basic buffers: These include a mixture of a weak base and salt formed of a strong acid.

Buffers do not accept any changes in pH of a given solution upon adding a tiny amount of OH or H+ ions.

It must be noted, however, that the pH of a buffer shows a change in the addition of OH- or H+ ions, but this change is significantly less than the change that would occur in the absence of a buffer.

Examples of Buffers 

The following example is for CH3COOH or CH3COO- :

When H+ is added to the buffer 

CH3COO- + H+ → CH3COOH

On the addition of OH- to the buffer

CH3COOH + OH- → CH3COO- + H2O

The main function of the buffer is to absorb the effect of H+ or OH-. 

Examples of buffers and their pKa (their acid strength):

Introduction to Buffering Capacity

The skill or ability to resist changes in the pH is referred to as the buffering capacity of a buffer in chemistry. The total moles of H+ should be added to 1 litre of the given buffer to decrease the pH of an allocated buffer by a single unit. The number of total moles of OH should be added to 1 litre of the given buffer to increase the pH of a buffer by a single unit.

The buffer capacity is the quantity of acid or base that a buffer can neutralise before the pH changes significantly. A greater buffer capacity indicates that more acid or base is neutralised before drastically changing the pH.

Increased buffer capacity at a constant level of acidity within a pH range of 6.0 to 9.0 can slow the corrosion rate in steels, exceptionally mild steels. However, increasing buffer capacity at different pH levels owing to increased alkalinity does not result in lower corrosion rates, as higher conductance and ionic strength do.

The primary function of buffers is to keep the pH of a given solution within a restricted range. The higher the amounts of OH- and H+molecules present in the buffer system, the less influence a strong base or acid has on the pH system. 

While the OH – determines the pH buffer and H+ ratio, the ability of a buffer to accept a strong base or acid is characterised by individual concentrations.

The buffer’s capacity is generally determined by the concentrations of the constituents in the buffered solution. The buffer solution will have a higher capacity if it is highly concentrated. It is normally determined using a technique called titration.

Buffer capacity is denoted with ‘β’.

Formula

The formula that is used to measure the buffer capacity of a buffer or solution in chemistry is as follows:

β = ∆A or ∆B∆pH

In the given formula:

β = is the symbol for buffer capacity 

∆A or ∆B = represents the amount of small increase in the number of moles of OH- or H3O+ that are added.

∆pH = represents the change in the pH of the buffer.

According to the buffer mentioned above in the capacity equation, the chemical solutions have a buffer capacity of one when one litre of it takes 1 gram equal to a strong acid or basic to modify the pH by one unit. 

As a result, the larger the buffer capacity, the less the pH shifts in a solution due to adding an acid or base, and vice versa.

Conclusion

Buffer solutions are those that can resist pH change when someone adds acid or base to it. These solutions have significant importance in acid-base chemistry. When it comes to the types of buffer solution, they are of two types. One is the acidic buffer solution, and the other is the alkaline buffer solution. The expression of the Henderson – Hasselbalch Equation is pH = pKₐ + log([A⁻]/[HA]). Buffer Capacity or Buffer Index is also an important part of studying buffer solutions.A greater buffer capacity indicates that more acid or base is neutralised before drastically changing the pH. There are several applications of buffers in the modern world.