Buffer pre.

1. Preparation of the Buffer solution
A buffer is an aqueous solution consisting of a mixture of a weak acid and salt of strong base. It
resists or pH changes very little when a small amount of strong acid or base is added to it. That is
used to prevent changes in the pH of a solution. There are no of buffer solution. But the best
example is the acetate buffer. This is formed by the equimolar ratio of acetic acid and sodium
acetate solution.

When acid added into buffer solution H
+
ions combine with CH3COO
-
to form
CH3COOH.similarly when we added few drops of base ,OH
-
ions react with acetic acid to form
water acetate ions. So there is no net increase of H
+
or OH
-.

You can change the pH of the buffer solution by changing the ratio of acid to salt, or by choosing
a different acid and one of its salts.
Buffer solutions are necessary to keep the correct pH for enzymes in many organisms to work. A
buffer of carbonic acid(H2CO3) and bicarbonate (HCO3
−
) is present in blood plasma, to maintain
a pH between 7.35 and 7.45.In synthetic biological reaction buffer is essential.
Industrially, buffer solutions are used in fermentation processes and in setting the correct
conditions for dyes used in coloring fabrics

Preparation of a buffer solution of a specific PH.
PH value of the Buffer solution can be find through Henderson equation;

2. PKa value is that value of PH in which conc. Of acid equal to conc. of salt.ph value depend upon
the ratio of salt and acid.

Procedure:
Prepare 1 liter 0.1M acetate buffer of pH 5.76. (PKa = 4.76)
Using Henderson equation we found the amount of sodium acetate and acetic acid required for
the preparation of buffer solution.


To prepared the 1M buffer in ratio of 10:1 we mixed 909 ml of salt solution(0.1M)and 90.9 ml of
acetic acid solution (0.1M).
0.1M solution of salt(CH3COONa) in 1000 ml = 82*0.1 = 8.2/liter

CH3COOH boatel concentration = 17.5M ; we wanted 0.1M concentration

So Appling
C1V1=C2V2 ; 17.5 * V = 0.1 * 1000
v= 1.71 for 0.1M solution that amount of acetic acid we dissolve in water to make a vol.
1000ml.

Discussion:
Using the Henderson Hasselbach equation we can prepare different buffer of the required
PH values. It is not necessary that the same PH come which you put in Equation. You can add
base add acid for the require PH vale.

References:
Lab manual in biochemistry by Arti Nigam.
http://www.chemguide.co.uk/physical/acidbaseeqia/buffers.html