Question

Explain buffer solution.

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Answer 1

$\large\bf{\underline{\underline{Question:-}}}$

Explain buffer solution.

$\large\bf{\underline{\underline{Answer:-}}}$

Buffer solution is a solution which resists the change in pH value when small amount of acid or base is added.

It is classified into two types. They are:-

• Buffer solution of single substance,
• Buffer solution of mixture.

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BUFFER SOLUTION OF SINGLE SUBSTANCE:

It is formed by mixing weak acid and weak base.

e.g. CH3COO + NH4OH$\longrightarrow$ CH3COONH4 + H2O

BUFFER SOLUTION OF MIXTURE:

It is again sub divided into two types:

a. Acidic buffer: It is the mixture of weak acid and salt of weak acid and strong base.

e.g. CH3COOH + CH3COONa

Here, CH3COOH is a weak acid and CH3COONa is a salt of weak acid and strong base.

b. Basic buffer: It is the mixture of weak base and salt of weak base and strong acid.

e.g. NH4OH + NH4Cl

Here, NH4OH is the weak base and NH4Cl is a salt of weak base and strong acid.

$\red{Hope \: it \: helps}$

Answer 2

Hola mate

Here is your answer -

Buffer Solutions

Buffers are solutions that resist a change in pH on dilution or on addition of small amounts of acids or alkali.

A lot of biological and chemical reactions need a constant pH for the reaction to proceed. Buffers are extremely useful in these systems to maintain the pH at a constant value. This does not mean that the pH of buffers does not change. It only means that the change in pH is not as much as it would be with a solution that is not a buffer.

Types of Buffer Solutions

Buffers are broadly divided into two types – acidic and alkaline buffer solutions. Acidic buffers are solutions that have a pH below 7 and contain a weak acid and one of its salts. For example, a mixture of acetic acid and sodium acetate acts as a buffer solution with a pH of about 4.75.

Alkaline buffers, on the other hand, have a pH above 7 and contain a weak base and one of its salts. For example, a mixture of ammonium chloride and ammonium hydroxide acts as a buffer solution with a pH of about 9.25. Buffer solutions help maintain the pH of many different things as shown in the image below.

Preparation of a Buffer Solution

If you know the pKa (acid dissociation constant) of the acid and pKb (base dissociation constant) of the base, then you can make a buffer of known pH by controlling the ratio of salt and acid or salt and base. Buffers can either be prepared by mixing a weak acid with its conjugate base or a weak base with its conjugate acid.

For example, phosphate buffer, a commonly used buffer in research labs, consists of a weak base (HPO42-) and its conjugate acid (H2PO4–). Its pH is usually maintained at 7.4.

Buffer Action

So, how does a buffer work? Let’s take the example of a mixture of acetic acid (CH3COOH) and sodium acetate (CH3COONa). Here, acetic acid is weakly ionized while sodium acetate is almost completely ionized. The equations are given as follows:

CH3COOH \rightleftharpoons  H+ + CH3COO–

CH3COONa \rightleftharpoons  Na+ + CH3COC–

To this, if you add a drop of a strong acid like HCl, the H+ ions from HCl combine with CH3COO– to give feebly ionized CH3COOH. Thus, there is a very slight change in the pH value. Now, if you add a drop of NaOH, the OH– ions react with the free acid to give undissociated water molecules.

CH3COOH + OH–  \rightleftharpoons  CH3COO– + H2O

In this way, the OH– ions of NaOH are removed and the pH is almost unaltered.

Solved Example for You

Question: Which of the following statement/s is false about buffer solutions?  

1. The pH of a buffer solution does not change on dilution.
2. Buffer solutions do not have a definite pH.
3. The pH of a buffer solution changes slightly on the addition of a small amount of acid or base.
4. The pH of buffer solution does not change on standing for long.

Solution:

The option ‘b’ is false. Buffer solutions have a definite pH.