Question

How do buffers resist pH change?

Answer 1

The measure of the acidity and basicity of the substance is nothing but the Ph of the substance. The solution is categorized into three types that are acidic, basic, or neutral depending on the pH of it. If pH less than seven then the solution is acidic and if the pH is greater than seven then the solution is basic. The solution with pH seven is neutral. pH is the negative logarithm of the hydrogen ion concentration.

Complete step by step answer:
Acidic buffer solution possesses acidic pH less than seven and it is formed from the weak acid and its salt with conjugate base. An example of an acidic buffer is a mixture of acetic acid and sodium salt of the acidic acid. Basic buffer possesses a pH greater than seven and it is a mixture of a weak base and its salt with conjugate acid. The example of the basic buffer is ammonium hydroxide and ammonium chloride.

If the acid is added to the solution then the ${{\text{H}}_3}{{\text{O}}^ + }$ of the acid is neutralized by the conjugate base of the buffer ${{\text{A}}^ - }$. The reaction is as follows:
${{\text{H}}_3}{{\text{O}}^ + }\left( {aq} \right)\, + \,{{\text{A}}^ - }\left( {aq} \right) \to {\text{HA}}\left( {aq} \right)\, + \,{{\text{H}}_{\text{2}}}{\text{O}}\left( l \right)$
In this way, the excess hydronium ions are converted into water and acid. In this pH of the solution is maintained.

If the base is added to the solution then the ${\text{O}}{{\text{H}}^ - }$ ions of the base are neutralized by the acid ${\text{HA}}$. The reaction is as follows:
${\text{HA}}\left( {aq} \right)\, + \,{\text{O}}{{\text{H}}^ - }\left( {aq} \right) \to {{\text{A}}^ - }\left( {aq} \right) + {{\text{H}}_{\text{2}}}{\text{O}}\left( l \right)$
In this way, the excess hydroxide ions are converted into water and a conjugate base. In this pH of the solution is maintained.

In this way, the buffer resists changing the pH of the solution.

Note: The solution which resists the change in pH of the solution is known as the buffer. Based on the buffer solution two main types of the buffer are acidic buffer and alkaline buffer solutions.
Acidic buffer solution possesses pH less than seven and the basic buffer solution possesses pH greater than seven.