Chemistry Forum

The antiseptic tincture of iodine is a solution of iodine and KI in ethyl alcohol(CH₃CH₂OH). When a sample of tincture of iodine weighing 5.000 g is diluted with water and titrated with 0.1500 M Na₂S₂O₃ solution, 19.75 mL of the latter is required. The reaction is

I₂ + 2 Na₂S₂O₃ → 2NaI + Na₂S₄O₆

What is the weight percentage of I₂ in the sample?

My answer: 19.75 mL of Na₂S₂O₃ is 0.0029625 mol of Na₂S₂O₃. So it requires 0.00148125 mol of I₂. Molar mass of I₂ =253.8 g.

So, we get 0.37594125 g per 5.000 g of sample of tincture of iodine. So, the weight percentage of I₂ in the sample is 7.519 %

Correct if the free I₂ is meant. As described its a solution of I₂ and KI what means KI₃, then the iodine of the salt is missing.

A solution of iodine and KI in ethyl alcohol means what. Would you give me examples of iodine of salt?

Here we have potassium triiodide

https://pubchem.ncbi.nlm.nih.gov/compou ... onohydrate

It is made by iodine and potassium iodide.

The whole compound is dissolved in alcohol.