What are buffers in chemistry? Types-examples and uses

Written by Adeel Abbas

A buffer is a solution that can resist a change in pH. It is able to keep the solution’s pH stable by taking small amounts of acid and base.

Specific and stable pH ranges are important for processes. Buffer solutions have a working pH range and capacity which dictate how much acid can be taken out before the pH changes.

Buffer is defined as the solution of reserve acidity or alkalinity which resists a change of pH after the addition of a small amount of acid or alkali. A constant pH is what is used to carry out many chemical reactions.

There are many systems that use buffering for pH regulation in nature. The bicarbonate buffering system is used to regulate the pH of blood, and it is also used as a buffer in the ocean.

Characteristics of buffer solution

  • It doesn’t have a change in its pH when standing for long periods of time.
  • It’s pH doesn’t change when you add it to water.
  • The addition of a small amount of an acid or base changes its pH.

 Composition of  buffer

A buffer consisting of a weak conjugate acid-base pair is required to maintain a pH range. Use either

a) A weak acid and its conjugate base 

b). The base and conjugate acid were

When preparing the buffer, the use of either one or the other is dependent on the desired pH. The following could be used as a buffer in the solution.

  • Acetic acid (weak organic acid w/ formula CH3COOH) and a salt containing its conjugate base, the acetate anion (CH3COO), such as sodium acetate (CH3COONa)
  • Pyridine (weak base w/ formula C5H5N) and a salt containing its conjugate acid, the pyridinium cation (C5H5NH+), such as Pyridinium Chloride.
  • Ammonia (weak base w/ formula NH3) and a salt containing its conjugate acid, the ammonium cation, such as Ammonium Hydroxide (NH4OH).

Types of Buffers

There are two types of buffer solutions…

1. Acidic buffer

Acid buffer solutions don’t have a pH higher than 7. It is usually made from a weak acid and a conjugate of it.

A mixture of ethanoic acid and sodium ethanoate in solution, which has a pH of 4.76 when mixed in equal concentrations, is commonly used in acidic buffer solutions. You can change the pH of the buffer solution by changing the ratio of acid to a salt or by choosing a different acid and one of its salts.

2. Basic / Alkaline buffer

The alkaline buffer solution is made from a weak base and one of its salts. An example of an alkaline buffer solution is a mixture of ammonia and Ammonia. The solution would have a pH of 9.25 if these were mixed together.

Hendersion’s Equation (pH of buffer)

(a) Acidic Buffer

It is a mixture of CH3COOH and CH3COONa


CH3COONa → CH3COO +  Na+

By the law of chemical equilibrium,  Ka = {[CH3COO] [H+]} / [CH3COOH]

∴ [H+] = {Ka [CH3COOH]} / [CH3COO]

Taking negative log both sides, we obtain that

– log[H+] = – log Ka – log {[CH3COOH]/[CH3COO]}

pH = pKa + log {[CH3COO]/[CH3COOH]}

pH = pKa + log {[salt] / [acid]}

This equation is known as Hendersion’s Equation

Where, Ka = dissociation constant

[CH3COO] = initial concentration of salt

[CH3COOH] = initial concentration of acid

Buffer Solution Examples

  • Acetic acid & conjugate base: CH3COOH & CH3COO
  • Formic acid & conjugate base: HCHO2 & CHO2
  • Pyridine & conjugate acid: C5H5N & C5H5H+
  • Ammonia & conjugate acid: NH3 & NH4+
  • Methylamine & conjugate acid: CH3NH2 & CH3NH3+

How do buffers work?

Buffers work by any added acid or base to maintain the moderate pH, making them a weak acid or base. An example of a buffer made up of weak base ammonia, NH3, and its conjugate acid, NH4+ is presented. The extra H+ ion added to the system is consumed by the NH3 to form NH4+.

The pH of the system doesn’t change much because all the extra H+ ion are locked up and have formed a weaker acid, NH4+. When NaOH is added to this buffer system, the ammonium ion donates a proton to the base to become ammonia and water, thus neutralizing the base without any significant pH change.

Breaking of buffer

The term “breaking of the buffer solution” is used when the entire base and its conjugate acid are consumed to eliminate the added acid.

The buffer’s pH will change quickly if an acid or base is added. The amount of acid or base a buffer can absorb is what determines its breaking capacity. It is to be noted that a solution with a weak base has a higher buffer capacity than a solution with a strong acid.

Applications of Buffer in chemistry

  • Industrial processes where Buffers are used include the manufacture of paper, dyes, ink, paints, drugs, and more.
  • Buffers are used in agriculture, dairy products, and the preservation of various types of fruits and vegetables.
  • Buffer is used to indicate the pH of indicators.
  • Blood is a natural buffer required to maintain the pH to sustain life.