MadSci Network: Chemistry

Re: Is mass conserved in a reaction between vinegar and baking soda?

Area: Chemistry
Posted By: Samuel Conway, Senior Staff Chemist, Avid Therapeutics,Philadelphia, PA
Date: Sun Jun 1 14:11:06 1997
Area of science: Chemistry
ID: 863484581.Ch
There are a few possible reasons for this.  One of them is *NOT* that the
mass of the reaction is not conserved!

1)  The plastic bag may not be perfectly air-tight, and some of your gas
    may be escaping.  

2)  Whereas carbon dioxide is indeed heavier than air, it is not so heavy
    that all of the molecules sit down on the surface of the liquid.  
    The gas is "floating", and thus is exerting a partial pressure on the
    inside of the plastic bag.  In other words, it's pushing up a little
    bit, and reducing the normal downward push of atmospheric pressure.

Because of this, using reactions that generate gas may not be the best
way to demonstrate conservation of mass.

I recommend using a solution of copper sulfate in one small flask and a
solution of barium chloride in another.  Place both on a balance and
check the mass, and then pour the two together.  Replace both flasks on
the balance and record the mass once more.  The reaction forms a nice 
heavy precipitate.

Current Queue | Current Queue for Chemistry | Chemistry archives

Try the links in the MadSci Library for more information on Chemistry.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network
© 1997, Washington University Medical School