Question

Calculate the concentration of the standardized thiosulfate solution.

The following are the steps and the concentration of my KIO₃ was 0.0114 and the weighed mass of Na₂S₂O₃ was 1.719 g

Weigh about 1.7 g Na₂S₂O₃  5H₂O, and transfer it to a 4 oz glass storage bottle. Add 100 mL (graduated cylinder) of room-temperature DI water, which has beenbubbled extensively with nitrogen, and which contains 100 mg /liter Na₂CO₃. Mix

thoroughly and add 1 drop of chloroform to prevent bacterial growth.

2) For the standardization, pipet 5 mL of the KIO₃ solution into each of three 125 mL Erlenmeyer flasks.  From this point treat each flask separately until the titration isfinished.  Make the calculation to estimate your approximate endpoint volume.

3) Add 0.5 g of solid KI and 2.5 mL of 0.5 M H₂SO₄ to the first flask, and immediately

begin titrating with the Na₂S₂O₃ solution.

THE VOLUME OF THIOSULFATE USED UP WAS 5.09 mL

Answer 1

Calculation of concentration of thiosulphate

     M of thiosulphate = ?

Molicular weight of the thio sulphate ( M.W) = 158.11g

Mass of the thiosulphate (W) = 1.719

Solution volume (V) = 100 ml

Formula for the concentration of thiosulphate

M = ×

M =   × =0.1087M

M=0.108

The concentration of thiosulphate is 0.108m in 100ml of DI water .

Standardisation of thiosulphate solution

Add the 1 drop of chloroform to the 100ml of sodiumthoisulphate 0.1087M to prevent the bacterial growth

The take 5ml of KIO₃ solution to each sample to standardise in the conical flask and also take the sodium thiosulphate (0.1087M) in the burette(50ml) run down the sodium thio sulphate into the conical flask drop by drop sodium ythio sulphate is 5.09ml consumed now calculate the concentration of sodium thio sulphate accurately.

N₁V_{1 =} N₂V₂

0.1087×5 = ? × 5.09

M

Here the accurate value of the sodium thiosulthate concentration is 0.1067M

1. 0.5 g of solid KI and 2.5 mL of 0.5 M H₂SO₄ this solution contains the molarity 1.2048 this is added to the first sample the consumption of thiosulphate is 5.09ml