Both sites say, in very similar words, that the way to calculate the density of water with 1% carbonation (by molecular concentration, it seems) is to take the weighted average:
0.99*density of water +0.01*density of CO
2 gas.
They get that dissolved CO
2 reduces the density by almost 1%, since the density of CO
2 gas is very low compared to water at atmospheric pressure.
It's a comical example of two bad habits:
1. copying other web sites thoughtlessly.
2. using formulas thoughtlessly.
They aren't even remotely close to getting the description right. The dissolved CO
2 isn't there as a bunch of little pockets of CO
2 gas. It's there as individual molecules and ions (some ionizes). Since CO
2 has a molecular weight about 2.5 times as big as H
2O, but doesn't occupy all that much more space, it actually raises the density, rather than lowering it. From looking up the experimentally observed partial molar volume of CO
2 in water, I get that instead of the density going down almost 1% for every 1% carbonation, it actually goes up about 0.37%.
Mike W.
(published on 04/15/2011)
