Crime Busters B

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christseeker
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Crime Busters - sodium acetate reaction with HCl/gypsum

Post by christseeker »

When coaching my kids for CB, they added HCl to sodium acetate, and it fizzed. Notes elsewhere said that it is not supposed to. What is going on?

When water is added to gypsum, ours turned into "oyster poop" color (shown in the link below). Is this always the case?

http://3.bp.blogspot.com/-g5S6Lt3ltjM/U ... G_6181.jpg
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Re: Crime Busters B

Post by AlphaTauri »

Hmm yeah, HCl + sodium acetate should not fizz to my knowledge... is it possible there was residue from some kind of carbonate in the test tube/container?

I have no idea about the gypsum though, sorry.
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Re: Crime Busters - sodium acetate reaction with HCl/gypsum

Post by samlan16 »

christseeker wrote:When coaching my kids for CB, they added HCl to sodium acetate, and it fizzed. Notes elsewhere said that it is not supposed to. What is going on?

When water is added to gypsum, ours turned into "oyster poop" color (shown in the link below). Is this always the case?

http://3.bp.blogspot.com/-g5S6Lt3ltjM/U ... G_6181.jpg
Sodium acetate should not fizz. I would recommend thoroughly cleaning your labware by hand, then testing again. (Perhaps the HCl reacts with dishwasher soap that violently, but I don't know how you're cleaning.)

As for the gypsum, I don't know what to say. Could it have been impure, or could it have reacted with residue? Calcium sulfate should retain its color when water is added.

Also, how much gypsum did you use? Be careful about giving your kids too much- proctors usually only give competitors a couple of grams of each sample as though they were collected from a crime scene.
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Re: Crime Busters B

Post by whovian11 »

about the gypsum, I think that you put too much of something in your test. also with sodium acetate it should not fizz but I think, from my memory, mine fizzed too but I'm not sure. after you do the tests and you can't identify something look in any and all sheets you have also check out sonic.org.
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Re: Crime Busters B

Post by samlan16 »

Pure speculation (pun intended), but this chemical distributor lists several impurities regularly found in their sodium acetate. Some of the listed ions, such as phosphate and sulfate, could be in compounds that spontaneously react with HCl. If you used acetate that is not up to food grade or industrial grade standards, this may be what caused your problem.
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Re: Crime Busters B

Post by sciolylover13 »

Does anyone know how to differentiate hydrogen peroxide and water? My coach said hydrogen peroxide should smell weird, but I can't tell the difference. :?
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Re: Crime Busters B

Post by Panda Weasley »

sciolylover13 wrote:Does anyone know how to differentiate hydrogen peroxide and water? My coach said hydrogen peroxide should smell weird, but I can't tell the difference. :?
Hydrogen peroxide will react with other certain substances (can't look any up right now but I know that there is one with baking soda). You can also sometimes see bubbles.
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Re: Crime Busters B

Post by samlan16 »

sciolylover13 wrote:Does anyone know how to differentiate hydrogen peroxide and water? My coach said hydrogen peroxide should smell weird, but I can't tell the difference. :?
The iodine test. KI should react slowly with the peroxide to form some gas, which means it will form bubbles after a while. Obviously, it will do nothing with water.
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Re: Crime Busters B

Post by sciolylover13 »

samlan16 wrote:
sciolylover13 wrote:Does anyone know how to differentiate hydrogen peroxide and water? My coach said hydrogen peroxide should smell weird, but I can't tell the difference. :?
The iodine test. KI should react slowly with the peroxide to form some gas, which means it will form bubbles after a while. Obviously, it will do nothing with water.
Ok thanks!
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Re: Crime Busters B

Post by whovian11 »

I'm not sure but I think that when you shake hydrogen peroxide there will be bubbles. you can always tell for a few things on just smell.
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