A buffer is a solution that can resist changes in pH when small amounts of an acid or base are added to it.
It does this by quickly reacting with the added acid or base to form a weak acid or base, which helps to maintain the pH of the solution within a narrow range.
Buffers are important in biological systems because they help control the pH of body fluids like blood and urine and make sure enzymes and other proteins work properly.
Without buffers, even small changes in the pH of these fluids could have significant impacts on the body’s overall health and well-being.
In this article, we’ll go into more detail about how buffers work, how they react, and how they can be used.
Principles of buffer action
Buffers are solutions that are able to resist changes in pH when small amounts of an acid or base are added to them. They work by reacting with the added acid or base to form a weak acid
a. Acidic Buffers
Acidic buffers are solutions that contain a weak acid and its conjugate base. The weak acid used in an acidic buffer is typically a monoprotic acid, such as acetic acid (CH3COOH), with a pK_a value in the range of 4-6. The conjugate base is the anion that is formed when the acid donates a proton, such as acetate (CH3COO–).
The pH of an acidic buffer can be calculated using the Henderson-Hasselbalch equation:
pH = pK_a + log([A^-]/[HA])
where [A^-] and [HA] are the concentrations of the conjugate base (A^-) and weak acid (HA), respectively, and pK_a is the acid dissociation constant.
b. Basic Buffers
Basic buffers are solutions that contain a weak base and its conjugate acid. The weak base used in a basic buffer is typically an amine, such as ammonia (NH3), with a pK_b value in the range of 9-11. The conjugate acid is the protonated form of the weak base, such as ammonium (NH4+).
The pH of a basic buffer can be calculated using a similar equation:
pH = pK_b + log([B]/[HB+])
where [B] and [HB+] are the concentrations of the weak base (B) and conjugate acid (HB+), respectively, and pK_b is the base dissociation constant.
c. Zwitterionic Buffers
Zwitterionic buffers are solutions that contain a compound that can act as both an acid and a base. These buffers are able to resist changes in pH over a wide range, and are commonly used in biological systems.
An example of a zwitterionic buffer is glycine (NH2CH2COOH), which has a pK_a of 2.3 and a pK_b of 9.6.
This allows glycine to act as both a weak acid and a weak base, depending on the pH of the solution.
Preparation of buffer solutions
The preparation of buffer solutions involves several steps, including calculating the molarity and concentration of the buffer components, selecting appropriate buffer components, and preparing the solution using the appropriate method.
Calculating molarity and concentration of buffer components
The first step in preparing a buffer solution is to calculate the molarity and concentration of the buffer components.
This can be done using the Henderson-Hasselbalch equation:
pH = pK_a + log([A^-]/[HA])
where [A^-] and [HA] are the concentrations of the conjugate base (A^-) and weak acid (HA), respectively, and pK_a is the acid dissociation constant.
To use this equation, you will need to know the desired pH of the buffer solution and the pK_a value of the weak acid being used.
Once the molarity of the weak acid and conjugate base has been calculated, the concentration of each component can be determined by dividing the molarity by the total volume of the buffer solution.
Selection of buffer components
When selecting buffer components, it is important to consider the pK_a value of the weak acid and the desired pH range for the buffer. The pK_a value should be close to the desired pH, as this will allow the buffer to resist pH changes over a wider range.
Buffer reactions
a. Addition of acid or base to buffer solution
When an acid or base is added to a buffer solution, the buffer will consume the excess acid or base, helping to maintain the pH of the solution within a narrow range. The amount of acid or base that can be added to a buffer before the pH starts to change significantly is known as the buffer’s capacity.
The capacity of a buffer can be calculated using the Henderson-Hasselbalch equation:
pH = pK_a + log([A^-]/[HA])
where [A^-] and [HA] are the concentrations of the conjugate base (A^-) and weak acid (HA), respectively, and pK_a is the acid dissociation constant.
b. Addition of solute to buffer solution
The addition of a solute to a buffer solution can also affect the pH of the solution. If the solute is an acid or a base, it will consume or produce protons, which will shift the equilibrium of the buffer and cause the pH to change. If the solute is neutral, it will not affect the pH of the solution.
c. Dilution of buffer solution
The dilution of a buffer solution can also affect its pH. When a buffer solution is diluted, the concentration of the weak acid and conjugate base decreases, which can shift the equilibrium of the buffer and cause the pH to change.
The extent of the pH change will depend on the initial concentration of the buffer and the degree of dilution.
Applications of buffers
Buffers are used in a variety of applications, including biological systems, industrial processes, and analytical chemistry.
a. Biological systems
- In biological systems, buffers play a crucial role in regulating the pH of bodily fluids, such as blood and urine.
- They help to maintain the pH of these fluids within a narrow range, which is necessary for the proper functioning of enzymes and other proteins.
- Buffers are also used in tissue culture media to maintain the pH of the medium and support the growth of cells.
b. Industrial processes
- Buffers are used in a variety of industrial processes to control the pH of solutions during chemical reactions.
- They are also used to stabilize pH in cleaning and personal care products, such as shampoos and toothpaste.
c. Analytical chemistry
- In analytical chemistry, buffers are used to calibrate pH meters and to maintain the pH of solutions during chemical analyses.
- They are also used in the preparation of standard solutions for titrations.
Overall, buffers are an essential tool in a wide range of applications due to their ability to resist changes in pH.
Conclusion
Buffers are solutions that are able to resist changes in pH when small amounts of an acid or base are added to them. They work by reacting with the added acid or base to form a weak acid or base, which helps to maintain the pH of the solution within a narrow range.
There are several types of buffers, including acidic buffers, basic buffers, and zwitterionic buffers. Buffers are used in a variety of applications, including biological systems, industrial processes, and analytical chemistry.
In conclusion, buffers are an essential tool for maintaining the pH of solutions in a wide range of applications. Further research is needed to develop new and improved buffers for use in various fields, including medicine, environmental science, and chemical manufacturing.
The development of novel buffer systems with improved stability and capacity will continue to be an active area of research in the future.
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