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Colors!!! Cant find in google!

Tucosalamanca01

What is the color of Na2s2O3 (sodium thiosulfate solution) and Na2S4O6 (Sodium tetrathionate solution)?

Reply 1

username986184

Original post by Tucosalamanca01

What is the color of Na2s2O3 (sodium thiosulfate solution) and Na2S4O6 (Sodium tetrathionate solution)?

Both colourless

Reply 2

Tucosalamanca01

Original post by TeachChemistry

Both colourless

Then why does Iodine solution turn pale yellow when thiosulfate is added to it? Is it because dilute iodine solution is pale yellow?

(edited 7 years ago)

Reply 3

Tucosalamanca01

Original post by TeachChemistry

Both colourless

Then why does Iodine solution turn pale yellow when thiosulfate is added to it? Is it because dilute iodine is pale yellow?

Reply 4

username986184

Original post by Tucosalamanca01

Then why does Iodine solution turn pale yellow when thiosulfate is added to it? Is it because dilute iodine solution is pale yellow?

The iodine solution is brown to start with. You titrate the iodine back to iodide. When there is a tiny bit of iodine left the mixture is very light yellow. At this point you add starch which complexes the iodine and goes blue. You then only have to add a few more drops of thiosulphate and the mixture becomes colourless.