Preparation and standardization of 0.05 M Hydrochloric acid EP Volumetric Solution

1.  PREPARATION :

Dilute 5.15 g of Hydrochloric acid to 1000 ml with water.

2. STANDARDISATION :

Dissolve 0.050 g of Sodium carbonate in 20 ml water, add 0.1 ml of Methyl orange solution and titrate with 0.05 M Hydrochloric acid until the solution just becomes yellowish-red. Boil for 2 minutes. The solution reverts to yellow. Cool and continue the titration until a yellowish-red colour is obtained.

1 ml of 0.05 M Hydrochloric acid is equivalent to 2.65 mg of Na2CO3.

3. CALCULATION :

 Molarity (M) = [0.05 x Weight of Sodium Carbonate (in g)]/ [Titration Reading (in ml) x 0.00265]

4. PREPARATION OF INDICATORS / REAGENTS :

a. Methyl orange solution :

Dissolve 0.1 g of Methyl orange in 80 ml of water and dilute to 100 ml with Ethanol (96%).

Test for sensitivity :  A mixture of 0.1 ml of the Methyl orange solution and 100 ml of carbon dioxide free water is yellow. Not more than 0.1 ml of 1 M Hydrochloric acid is required to change the colour to red.

Colour change : pH 3.00 (red) to pH 4.40 (yellow).

5. STORAGE CONDITION :

Store in glass-stoppered bottles.

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