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Topic: How would you test for these gases?  (Read 10826 times)

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Offline jgaoxx06

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How would you test for these gases?
« on: June 06, 2006, 01:41:33 PM »
Hi,

Can anyone tell me how you would test for oxides of sulphur and nitrogen dioxide? I've searched on chemguide and Google, but didn't find anything. I know you use glowing splint for oxygen and limewater for carbon dioxide, but I'm stuck on these two gases.

Offline anarchron

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Re: How would you test for these gases?
« Reply #1 on: June 06, 2006, 04:50:03 PM »
Sniff it.
Sulphur dioxide will stink.
Nitrogen Dioxide will make you laugh.

Offline Borek

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Re: How would you test for these gases?
« Reply #2 on: June 06, 2006, 05:11:47 PM »
Nitrogen Dioxide will make you laugh.

Will make you dead.
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Offline Will

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Re: How would you test for these gases?
« Reply #3 on: June 06, 2006, 06:41:52 PM »
Can anyone tell me how you would test for oxides of sulphur and nitrogen dioxide? I've searched on chemguide and Google, but didn't find anything. I know you use glowing splint for oxygen and limewater for carbon dioxide, but I'm stuck on these two gases.

Oxides of sulfur:
  • Have no color
  • Turn damp blue litmus paper red
  • Have a choking, lung-catching smell

and  SO2 turns filter paper soaked in orange potassium dichromate(VI) solution green without the deposition of Sulfur, which is what H2S does. I don't know about a specific test for SO3, although I know lots of things it can do, just not on the scale of testing.

NO2 has a very characteristic brown color which darkens on heating, and if, when it is dissolved in water and ammonium chlorde is added, a gas (which is N2- you can test for that too as it does gives a negative result for every single test that I know of!) is evolved, then it is definately NO2. If you still aren't 100% sure its NO2 for whatever reason then you can always check its not bromine as it will do nothing when it is dissolved in water and AgNO3(aq) is added. (Bromine would give cream precipitate).

NO2 has a choking smell, it certainly won't make you smile, let alone laugh!

Offline pantone159

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Re: How would you test for these gases?
« Reply #4 on: June 06, 2006, 07:17:27 PM »
Nitrogen Dioxide will make you laugh.

You are thinking of N2O, nitrous oxide.

Offline mike

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Re: How would you test for these gases?
« Reply #5 on: June 06, 2006, 08:28:50 PM »
Sniff it.
Sulphur dioxide will stink.
Nitrogen Dioxide will make you laugh.

Never do this test!
There is no science without fancy, and no art without facts.

Offline jgaoxx06

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Re: How would you test for these gases?
« Reply #6 on: June 07, 2006, 08:02:30 AM »
Wow, thanks everybody, you're all so helpful. :)

Offline Alberto_Kravina

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Re: How would you test for these gases?
« Reply #7 on: June 07, 2006, 10:34:07 AM »
An easy (and safe) detection reaction of sulfur dioxide is to pass the unknown gas in H2O2. If there is SO2 it reacts with H2O and forms sulfuric acid which can be easily detected with Ba2+

Offline qlabel

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Re: How would you test for these gases?
« Reply #8 on: June 07, 2006, 10:45:38 AM »
Quote
Never do this test!
Is it possible to do it carefully, or is it too dangerous? ???

Is it also possible to make a quantitative analysis with the method you described AK? :)

Offline Mitch

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Re: How would you test for these gases?
« Reply #9 on: June 07, 2006, 10:54:20 AM »
Never sniff unknown gasses!
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Offline Alberto_Kravina

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Re: How would you test for these gases?
« Reply #10 on: June 07, 2006, 10:58:29 AM »
Quote
Is it possible to do it carefully, or is it too dangerous?
That can be pretty dangerous...don't try it :P

Quote
Is it also possible to make a quantitative analysis with the method you described AK?
I don't know, you could titrate the formed sulfuric acid with NaOH, however, I don't know if 100% SO2 absorbs to the H2O2...so I'm definately not sure about the accuracy of this method

Offline Mitch

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Re: How would you test for these gases?
« Reply #11 on: June 07, 2006, 11:39:32 AM »
Just take an IR if possible.
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Offline Will

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Re: How would you test for these gases?
« Reply #12 on: June 07, 2006, 06:08:35 PM »
Quote
Never do this test!
Is it possible to do it carefully, or is it too dangerous? ???

Not only is it dangerous, but it is completely inaccurate. There are many gases that stink- ammonia, H2S, Cl2, hydrogen halides, C(SH)2(Me)2, thioacetone, (E)-but-2-ene-1-thiol, the list goes on and on.

Just take an IR if possible.
But that doesn't really count as a test, though, does it? ???

Offline bramgo

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Re: How would you test for these gases?
« Reply #13 on: June 07, 2006, 08:05:15 PM »
There are kits to do these kind of test. I did both an NOx and a SOx test about 4 months ago. Both are like little glass tubes. First you need to break of the top and next you need to suck air inside them with some kind of pump. Fast, clean and easy. :)

Offline Will

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Re: How would you test for these gases?
« Reply #14 on: June 07, 2006, 08:21:40 PM »
There are kits to do these kind of test. I did both an NOx and a SOx test about 4 months ago. Both are like little glass tubes. First you need to break off the top and next you need to suck air inside them with some kind of pump. Fast, clean and easy. :)

Oooo cool :o! But isn't that cheating :P!? I think  jgaoxx06 wanted to know about a specific chemical test for NO2 and oxides of sulfur. My teachers wouldn't have been too impressed if I told them that a test for these gases was to test them with specific kits which test for the gas in question! ;)

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