jenicalina Posted August 19, 2014 Report Share Posted August 19, 2014 I know when you perform a classic iodine clock reaction, the reacting solution is meant to turn blue-black. However, when I performed it... not only did it not turn blue black, but instead--- brown?! In my experiment, I added two different solutions: Solution 1 contained:20mL of a reacting solution (1.5g of KI added to 1.9g of Na2S2O3 in 250cm3 of water)10mL sulfuric acid (H2SO4)2mL of dilute starch solution Solution 2 contained:Distilled waterVariable volumes of hydrogen peroxide (H2O2) Did I do something wrong? I've processed the data that I've collected, and my trends are looking fine, however I just don't know why my solution turned brown-black instead of blue-brown, nevertheless explain this in my conclusion. If it helps, the reaction did smell.... Could it be that the reaction that I did wasn't really an iodine clock at all..? Any help or suggestions would be greatly appreciated!! Reply Link to post Share on other sites More sharing options...
Ossih Posted August 19, 2014 Report Share Posted August 19, 2014 Maybe you didn't have enough starch? That's sort of unlikely but starch does turn completely black/blue in the presence of Iodine. Or possibly, your KI was impure. I can't think of anything else. Reply Link to post Share on other sites More sharing options...
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