Principles of Biochemistry (2+1)

Preparation of Standards

Definition

1.Atomic Weight

• Atomic weight of an element is the relative weight of the atom on the basis of oxygen as 16.
• E.g. Atomic weight of sodium is 23.

2.Molecular Weight

• The sum of atomic weights of all the atoms in a molecule is its molecular weight
• E.g. Molecular weight of H₂SO₄ is 98, Since-Hydrogen 2x1=2; sulphur 1x32=32;Oxygen 4x16=64; T=98

3.Equivalent weight

• Equivalent weight of a substance is the number of grams of the substance required to react with, replace or furnish one mole of H₂O+ or OH. The equivalent weight of an acid is the weight that contains one atomic weight of acid hydrogen i.e., the hydrogen that reacts during neutralization acid with base.

4. Buffer

            ·    A solution containing both a weak acid and its

                conjugate base which tends to resist change in pH 

                when small amount of acid or base is added.

5. pH

• pH is a value taken to represent the acidity or alkalinity of an aqueous solution.
• It is defined as logarithm of the reciprocal, of the hydrogen ion concentration of the solution. i.e. pH=log 1/[H+].

6.Dilute acids

• While preparing dilute acids, add acid slowly to water preferably under cooling.
• Alkali solutions: when preparing concentrated alkali solutions, (e.g., 40% NaOH) dissolve the alkali in distilled water under cooling.

7. Water

• In biochemical experiments, it is advised to use Distilled water.