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The Environment / Why Does CO2 Escape From An Enclosure More Easily Than Air?
« on: 27/05/2011 12:21:02 »
I am following up on what Pete Ridley was asking about regarding the size of the different air molecules http://www.thenakedscientists.com/forum/index.php?topic=38675.0. I think that most of us know that ordinary party balloons filled with He deflate more quickly than ones we blow up ourselves because the He molecule is smaller than other gases in the air and escapes more easily through pores in the usual latex rubber balloon. I found a question that was asked a couple of years ago about CO2 seeming to escape from a latex balloon even faster than He does http://www.natscience.com/Uwe/Forum.aspx/chem/9671/carbon-dioxide-filled-latex-balloons.
The discussion there wandered off elsewhere without really answering the original question, a bit like what happened to Pete Ridley’s question here, but one person did give a link to a book
I decided to try a similar experiment with balloons, filling one with CO2 from vinegar and baking powder (bicarb) and blowing up the other by mouth. Although I haven’t done this in a properly scientific way my simple experiment has shown that on both occasions when I filled two apparently identical latex balloons to about the same size (about 120mm diameter) the one filled with CO2 shrank to less than 100mm in a couple of days while the one that I blew up stayed almost unchanged. That gives a CO2 diffusion rate through the balloon of about 1cc/min.
When I get my hands on a CO2 bottle I’ll do a more scientific experiment and record the conditions and results carefully but in the meantime can anyone explain why CO2 seems to escape through a continer when ordinary air doesn’t. In his comment on the 20th April Pete Ridley talked about Professor Nisbett having trouble storing CO2 but not CH4 and that CO2 was like a needle http://www.thenakedscientists.com/forum/index.php?topic=38675.50 so maybe shape as well as size is important.
The discussion there wandered off elsewhere without really answering the original question, a bit like what happened to Pete Ridley’s question here, but one person did give a link to a book
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Irwin and Rippe's intensive care medicinehttp://books.google.com/books?id=IhDFIj-PoucC&pg=PA48&lpg=PA48&dq=balloon+latex+diffuse+rapidly+co2+OR+carbon-dioxide&source=web&ots=_Ib_fjHAbh&sig=jf7hwFKOF9x_%3Cbr%3Erx89W2c5UAZ3BDw&hl=en&ei=UXePSaPrOYzQMcORoZEL&sa=X&oi=book_result&resnum=5&ct=re%3Cbr%3Esult#v=onepage&q&f=false that says on page 48/49
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carbon dioxide defuses through a latex balloon at a rate of approximately 0.5cc per minute
I decided to try a similar experiment with balloons, filling one with CO2 from vinegar and baking powder (bicarb) and blowing up the other by mouth. Although I haven’t done this in a properly scientific way my simple experiment has shown that on both occasions when I filled two apparently identical latex balloons to about the same size (about 120mm diameter) the one filled with CO2 shrank to less than 100mm in a couple of days while the one that I blew up stayed almost unchanged. That gives a CO2 diffusion rate through the balloon of about 1cc/min.
When I get my hands on a CO2 bottle I’ll do a more scientific experiment and record the conditions and results carefully but in the meantime can anyone explain why CO2 seems to escape through a continer when ordinary air doesn’t. In his comment on the 20th April Pete Ridley talked about Professor Nisbett having trouble storing CO2 but not CH4 and that CO2 was like a needle http://www.thenakedscientists.com/forum/index.php?topic=38675.50 so maybe shape as well as size is important.