Question

What is buffer solution.How many types of buffer are there. How to calculate pH in each cases.What is buffer capacity ?​

Answer 1

BUFFER SOLUTION

It is a solution which resist change in pH.We change pH by changing hydrogen ion concentration or by changing hydroxide ion concentration or by mixing water .By buffer solution, we don't mean that there would be no pH change at all, we mean change would not be corresponding to the changes done

For example :- If we add 10 moles of hydrogen ion , pH change would be corresponding to 2 moles and not that of 10 moles.

TYPES OF BUFFER SOLUTION

• There are two types of buffer solution.

Acidic Buffer Solution

It is a solution of weak acid and salt of weak acid with a strong base.

For example :- $CH _{3}COOH \: and \: CH _{3}CO {O}^{ - } {Na}^{ + }$

we calculate pH in this case using the formula

$pH= p k_{a} + log( \frac{salt \: concentration}{acid \: concentration} )$

Basic Buffer solution

It is a solution of weak base and salt of that weak base with a strong acid.

For example :- $NH_{3} \: and \: N { H_{4} }^{ + } {Cl}^{ - }$

we calculate pH in such cases by

$pH =14 - p k_{b} - log( \frac{salt \: concentration}{base\: concentration} )$

Buffer capacity

Buffer capacity is defined as the number of moles of H+/OH- ions added to one litre of the solution per unit change in pH.

Buffer capacity =

$\frac{Number of moles of H+ or OH- ions added to one litre of the solution}{change in pH}$