Topic: Function of starch solution(1) (Read 25269 times)

kylon · « **on:** July 17, 2007, 07:48:16 PM »

When having an experiment "rate law of an iodine clock reaction", a starch solution is added. What is the function of starch solution?
Thank for help first...

Yggdrasil · « **Reply #1 on:** July 17, 2007, 07:58:39 PM »

The starch is likely acting as an indicator for the presence of triiodide ion. Starch and triiodide form a complex which gives the solution a deep blue-black color.

http://en.wikipedia.org/wiki/Iodine_clock_reaction

kylon · « **Reply #2 on:** July 18, 2007, 05:04:14 AM »

Sorry, I miss some important things.
The experiment is using sulfuric asid, potassium iodine, thiosulfate, starch solution and distilled water.

The equations are:

H₂O₂ + 2I^- + 2H₃O⁺
---> I₂ + 4H₂O

I₂ + 2S₂O₃^2- ----> S₄O₆^2- + 2I^-

there are no triiodine ion.

AWK · « **Reply #3 on:** July 18, 2007, 05:59:27 AM »

http://www.elmhurst.edu/~chm/vchembook/548starchiodine.html

Borek · « **Reply #4 on:** July 18, 2007, 06:59:28 AM »

Quote from: kylon on July 18, 2007, 05:04:14 AM

I₂ + 2S₂O₃^2- ----> S₄O₆^2- + 2I^-

there are no triiodine ion.

Yes, there is

It is present in the solution whenever you have both I₂ and I^-

I₂ + I^- <--> I₃^-

Topic: Function of starch solution(1) (Read 25269 times)

kylon

Function of starch solution(1)

Yggdrasil

Re: Function of starch solution(1)

kylon

Re: Function of starch solution(1)

AWK

Re: Function of starch solution(1)

Borek

Re: Function of starch solution(1)

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