[cshieh1231]

I have to make 0.1 N of sodium thiosulphate from sodium thiosulphate anhydrous (158.11 g/mol) to react with 0.1 iodine solution.


I thought the equation is

Na₂S₂O₃ + I₂  2 NaI + 2 Na₂S₄O₆

Some website said Sodium Thiosulphate has 1:1 ratio for molarity : normaility.

I don't know why sodium thiosulfate only use one sodium to react with iodine.

[Borek]

Your reaction is not balanced. Could be a typo.

I don't know why sodium thiosulfate only use one sodium to react with iodine.

Sodium? Sodium is just a spectator.

What is normality of 0.1M I₂ solution?

[cshieh1231]

Your reaction is not balanced. Could be a typo.

I don't know why sodium thiosulfate only use one sodium to react with iodine.

Sodium? Sodium is just a spectator.

What is normality of 0.1M I₂ solution?

Ya it was a typo

2 Na2S2O3 + I2   2 NaI + 2 Na2S4O6

the normality of Iodine solution is 0.1 N

What I was trying to do is finding the % Sodium Lauryl Sulfate experiement.

In the wet analytical chemistry book instructed me to first run a blank experiment.  In a 50 ml water, add in 10 ml acetic acid, then add 10 ml of 0.1 N iodine solution.  (I think the acetic acid just making the water acidic, so the iodine would not react with water).  Then titrate the solution with 0.1 N of Na₂S₂SO₃.

Then in the second run.  Add 2.0 g of sodium lauryl sulfate (SLS) solution in the water/iodine/acetic acid solution.  Suppose the SLS's sodium will react with the iodine in the solution before the titration.  Therefore, we should actually use less of 0.1 N Na₂S₂SO₃ to titrate the iodine solution.

I was going to run a couple standards of 5%, 10%, 15%, 20%, and 30% of SLS solution, then make the calibration curve to compare my sample.

But now i am running into some quesitons.

1. How do I get the 0.1 n of Na₂S₂SO₃ solution? The F.W. is 158.11 g/mol. I want to make into 500mL.

So I was using 0.5 * 0.1 = 0.05 mol.  Then I don't really know why in this case, everyone said 0.1 N of Na₂S₂SO₃ equals to 0.1 M Na₂S₂SO₃.

2. Since I really am just making a calibration curve, I suppose that even if I miscalculated the concertration of Na₂S₂SO₃, I would still be okay because I am just using the amount of my Na₂S₂SO₃ solution need to titrate the left over iodine in the solution after it react with SLS.  However, I still can't get the curve right...

[Borek]

What is normality of 0.1M I₂ solution?

the normality of Iodine solution is 0.1 N

Is it? How many electrons does one I₂ molecule need?

http://www.titrations.info/iodometric-titration