Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: kylon on July 17, 2007, 07:48:16 PM
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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...
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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
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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 + 2S2O32- ----> S4O62- + 2I-
there are no triiodine ion.
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http://www.elmhurst.edu/~chm/vchembook/548starchiodine.html
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I2 + 2S2O32- ----> S4O62- + 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-