Problem with Procedure

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Problem with Procedure

Postby floringr » Fri Jan 11, 2013 8:55 am

I am doing a project on here that is not working procedure wise. It's "Presto! From Black to Clear with the Magic of Photochemistry". I did a test run of the experiment, but the solution did not change color, even after a few days. At first, I thought that the problem was that I didn't let the oxalic acid crystals dissolve. But that was because they just weren't dissolving, even after half an hour. So in the next test run, I found that I could get the crystals to dissolve under hot water. I ran the experiment that way, and it was better. It started out darker than the last testrun, and did get light. Yet, it kind of froze at just a lighter shade of orange, when it's supposed to be almost clear. I e-mailed a chemist for suggestions on how to make it work, and I did her suggestions, and yet, it still didn't change color. I tried adding more oxalic acid, putting it directly under a light, and heating up the solution before putting in the iodine. I tried all different combinations of these, and yet they still didn't work. They just stayed the same color. I am running out of ideas on how to make this work.

This is my equation for the experiment:
2 (NH4)+ + C2O4- + I2 → 2 (NH4)+ + 2 I- + 2 CO2

(NH4)+ = Ammonium ion
C2O4- = Oxalate ion
I2 = Iodine (orange to black)
I- = Iodide ion (colorless)
CO2 = Carbon dioxide

If there are any questions about the procedure, please go to the science buddies page of this experiment. I'm practically doing the same procedure.
Thanks!

*NOTE: I am actually in 8th grade, and am not doing the project it says im doing anymore. I can't figure out how to change it.
floringr
 
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Project Question: What is the depth to diameter ratio of simple impact craters on Mercury?
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Re: Problem with Procedure

Postby ChiaraB » Fri Jan 11, 2013 9:26 pm

Hello,
It seems like you are frustrated by this experiment , but it also seems like you have put a lot of thought and hard work into it. Though the written procedure might make it seem like all the iodine should be converted to iodide and you don't feel like you're getting the "right" results, what's most important when repeating an experiment is carefully following the given procedure, accurately collecting and recording the data, and thoughtfully analyzing the results. You wrote that you followed the procedure and even consulted a chemist and then performed variations of the original experiment. I would also suggest heating up the solution and adding more ammonium oxalate, but it seems that you have already tried those things. Other procedures for this experiment like this one http://www.woodrow.org/teachers/ci/1986/exp32.html use an even greater ratio of iodine to ammonium oxalate than the Sciencebuddies procedure. Carefully repeat the experiment as many times as possible - it is the best way to improve your results. If you are confident in the integrity of your experiments and the results and you feel that you have thoroughly investigated this problem, then report the results as you found them. Present all of the combinations of factors that you tried, and honestly report the outcomes. Is not the purpose of an experiment to yield some results that you didn't expect?
ChiaraB
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Project Question: Science Buddies Mentor
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