Question

A small amount of acid is added to a buffered solution. what will happen

Answer 1

Buffer is a solution which resist the change in pH with addition of small amount of acid or base.

Hence when small amount of acid is added to buffer its pH will not change, as the buffer has the capacity to resist the change in pH on small addition of acid or base to it.

Buffer is mixture of weak acid/base and its conjugate base/acid.

Hence when small amount of acid is added to HA/A-. The H+ ions added reacts with the conjugate base A- in buffer forming the weak acid and thus keeping the pH same.

Answer 2

The pH of the buffer solution will not change when a small amount of acid is added to it.

Further Explanation:

Buffer solution:

It is an aqueous solution of a weak acid and its conjugate base or a weak base and its conjugate acid. Buffer solutions are known to resist any change in their pH on the addition of strong acid or base. So these solutions are used where there is requirement of constant pH. Buffers are used in brewing industries, baby lotions, shampoos and in blood to maintain the pH of body near 7.4.

Types of buffers solutions:

1. Acidic buffer

The solutions that have a pH of less than 7 are known as acidic buffers. These consist of a weak acid and its conjugate base. A mixture of acetic acid and sodium acetate is an example of an acidic buffer.

2. Alkaline buffer

The solutions having a pH of more than 7 are called alkaline or basic buffers. These consist of a weak base and its conjugate acid. A mixture of ammonium chloride and ammonium hydroxide is an example of a basic or alkaline buffer.

Consider an example of a buffer solution of acetic acid and sodium acetate. The acetic acid is a weak acid so it ionizes only partially. The dissociation reaction of acetic acid is as follows:

${\text{C}}{{\text{H}}_3}{\text{COOH}}\left( {aq} \right) \rightleftharpoons {\text{C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ - }\left( {aq} \right) + {{\text{H}}^ + }\left( {aq} \right)$  

The dissociation reaction of sodium acetate is as follows:

${\text{C}}{{\text{H}}_{\text{3}}}{\text{COONa}}\left( {aq} \right) \to {\text{C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ - }\left( {aq} \right) + {\text{N}}{{\text{a}}^ + }\left( {aq} \right)$  

If any acid is added to the above buffer solution, the ${{\text{H}}^ + }$ ions released by it react with ${\text{C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ - }$ ions and undissociated acetic acid is produced according to the following reaction:

${\text{C}}{{\text{H}}_{\text{3}}}{\text{CO}}{{\text{O}}^ - }\left( {aq} \right) + {{\text{H}}^ + }\left( {aq} \right) \to {\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\left( {aq} \right)$

So the added acid is consumed by the acetate ions and therefore the pH of this buffer solution remains the same. It does not change on the addition of small amount of acid.

Learn more:

1. Write the chemical equation responsible for pH of buffer containing ${\text{N}}{{\text{H}}_{\text{3}}}$ and ${\text{N}}{{\text{H}}_{\text{4}}}{\text{Cl}}$ : brainly.com/question/8851686
2. Reason for the acidic and basic nature of amino acid. brainly.com/question/5050077

Answer details:

Grade: Senior School

Chapter: Buffer solutions

Subject: Chemistry

Keywords: pH, buffers, resist, change in pH, weak acid, conjugate base, weak base, conjugate acid, constant pH, CH3COOH, H+, CH3COO-, Na+, CH3COONa, acetic acid, sodium acetate.