Buffer solution

The literal meaning of buffer is that the person or thing that bears the shock. “The solution that resists the change in its pH when a small amount of acid or base is added is called a buffer solution”. 

Characteristics of buffer solution

• It has a definite value of pH
• pH does not change on further dilution or standing for a long time, by maintaining the conditions that the atmospheric gases do not absorb in this solution, or the walls of containers do not absorb in this solution.
• pH of buffer is affected by a change in temperature.
• An effective buffer has a pH in the range of 3-11
• On addition of a small amount of an acid or base creates small changes in the buffer solution, but overall pH remains intact.

Types of buffers

There are two main types of buffers

1. Acidic buffer    2) Basic buffer

In addition to this, there is also a third type, which is called a salt or neutral buffer.

Acidic buffer

These buffers are called acidic buffers because these buffer contain a pH less than 7. These buffers are formed by mixing two compounds. One compound is the weak acid, and the other compound is the salt of this weak acid with a strong base. For example, an acidic buffer contains CH₃COOH and CH₃COONa. These compounds ionize in water as shown by the following equation

CH₃COOH ⇌ CH₃COO^– + H⁺

CH₃COONa → CH₃COO^– + Na⁺

In this buffer system, three ions are predominantly present: weak acid (CH₃COOH), conjugate base CH₃COO^–, (the species that differ with each other based on their H⁺ ions is called conjugate base), and hydronium ion H⁺. Similarly, carbonic acid (H₂CO₃) and Na₂CO₃ are other buffer systems, which ionize as

H₂CO₃ ⇌ CO₃^-2 + 2H⁺

Na₂CO₃ →CO₃^-2 + 2Na⁺

In this system, the predominant ions are carbonic acid (H₂CO₃) and its conjugate base (CO₃^-2 ) and hydronium ions (H⁺). Thus, we can say that a buffer system contains a weak acid and its conjugate base. The weak acid accommodates OH^– ions of any base (by the formation of water), and the conjugate base accommodates the H⁺ ions of any acid.

Basic buffer

The buffer solution, which has a pH greater than 7, is called a basic buffer. It is formed by the combination of a weak base and the salt of this weak base with a strong acid. For example, a mixture of NH₄OH and NH₄Cl is an example of a basic buffer. This buffer ionizes in the following way,

NH₄OH ⇌ NH₄⁺ ₊ OH^–

NH₄Cl  → NH₄⁺ ₊  Cl^–

Neutral buffer

In a neutral buffer, the pH is close to 7, i.e., the concentration of hydrogen (H⁺) is equal to (OH^–). A neutral buffer is made by mixing

• A weak acid + its conjugate base. Or
• A weak base + its conjugate acid

For example, phosphate buffers with dihydrogen phosphate and hydrogen phosphate can maintain a pH near 7. Similarly, the bicarbonate buffer system (H₂CO₃/HCO₃^–) helps keep blood pH around 7.35-7.45.

These neutral buffers are especially important in biological systems like blood plasma, where enzymes need a stable, nearly neutral pH to function properly. In the laboratory procedures also used a precise neutral pH.

Henderson’s equation. The equation that is used to determine the pH/pOH of a buffer solution or the equation that is used to prepare the buffer solution of desired pH, is called Henderson’s equation.

Buffer capacity. The capacity of the buffer resists changing in its pH.

Best buffers. Those buffers are called best buffers, which have the best tolerance ability, and it is prepared by taking equal concentrations of acid and salt. For example, in the case of an acidic buffer, if we take 1 molar salt, then this buffer will be an excellent buffer. Or that buffer will be the best buffer in which the pH of the solution = pKa of the solution. According to Henderson’s equation, pH = pKa + log[salt/acid]. Thus, pH = pKa (log 1 = 0, log 10 =1, log 100 =2.         

Uses of buffer solution

• Our body uses buffers to maintain a blood pH of 7.35 to 7.45, and also in a massive number of biochemical reactions involving enzyme activities, metabolism, and respiration.
• Used in the biological experiments in the lab, also used in analytical procedures like titrations, reaction rate studies, and for calibration of pH meters
• Many industrial processes need buffer solutions, particularly fermentation, controlling dye processes, and manufacturing pharmaceuticals.  
• In research, buffer systems are used for biochemical assays.
• In the food industry, buffer systems are particularly used for maintaining the pH of food like cheese, yogurt, bakery products, and beverages. It also helps with food preservation, improves flavor, texture, and shelf life.
• In cosmetics preparations, buffer systems help to maintain the pH in shampoos, toothpaste, and creams.
• Buffer solutions are also used in drinking water and wastewater treatment. It prevents corrosion of pipes and improves treatment efficiency.