How to prepare and Standardize 0.1 N Sodium Thiosulphate volumetric Solution.

How to prepare and Standardize 0.1 N Sodium Thiosulphate volumetric Solution.

                                                              

                                                                     

Preparation of 0.1 N Sodium Thiosulphate volumetric solution.

➤ Glass ware and instruments required.

Beaker, Glass stirrer, Graduated Pipettes, Graduated cylinder, Analytical balance, Sucker, Volumetric flask, Conical flask, Burette, Fume hood.

➤ Reagents required.

Sodium Thiosulphate 

Molecular Wt. :- Na2S2O3,5H2O, 248.19

Potassium Bromate PS

Sodium Carbonate Reagent grade

Starch Indicator 

 ➤ Preparation.

Weigh accurately about 26 g sodium thiosulphate reagent grade and 0.2 g sodium carbonate reagent  grade in 1000 ml volumetric flask. Dissolve and dilute with recently boiled and cooled water. Filter the solution, if it is not clear.

➤ Standardisation.

Accurately weigh about 0.2 g Potassium Bromate PS into 250 ml volumetric flask. Dissolve and makeup the volume with recently boil and cooled water. Pipette out 50 ml of above solution into 250 ml conical flask. To this add 2 g potassium iodide reagent grade and 3 ml of 2 N Hydrochloric acid and slowly titrate with 0.1 N / 0.1 M Sodium Thiosulphate solution using starch solution as an indicator, which is added towards the end of the titration, until the blue colour is discharged. Note this final end point as burette reading in ml. 

➤ Calculations.

                                      g  KBrO₃  x  0.1 x 50

N / M = --------------------------------------------------------------

                           0.002784  x   Burette reading in ml x 250