# If carbon dioxide is non polar, why does it react with water?

I’ve read in many places that carbon dioxide forms carbonic acid with water since the carbon is partially positive and thus the oxygen bonds with it. But isn’t carbon dioxide in its entirety non polar since the 180 angle removes any dipole moment, so how would oxygen be attracted to the carbon?

Is it that individually each atom has partial charge but not collectively? Or am I wrong in some way?

• Fluorine gas is about as non-polar as you can get, but you don't want to mix it with water (or anything else...). Meanwhile, caesium fluoride is extremely polar, but happily dissolves in water with no reaction, and can be completely recovered by drying. – Nicolau Saker Neto Jun 3 at 10:56
• Carbon dioxide is pretty polar. True, it has zero dipole moment, but that's irrelevant. – Ivan Neretin Jun 3 at 11:05
• There is need to distinguish polarity of the whole molecule and polarity of its parts. CO2 as a molecule us not polar ( but is polarizable), but CO bonds are polar. – Poutnik Jun 3 at 12:30
• – Mithoron Jun 3 at 13:18
• Related: Why is carbon dioxide nonpolar? – Martin - マーチン Jun 3 at 15:47

I can only repeat myself here: Polarity is an ill-defined concept that has a nice potential for confusion.

In most cases, when specifying a molecule as polar, one is colloquially referring to the presence of an dipole moment, i.e. one actually categorises the molecule as dipolar. As described by ron in "Why is carbon dioxide nonpolar?", $$\ce{CO2}$$ has no dipole moment, it is therefore not dipolar, or colloquially it is not polar.

However, $$\ce{CO2}$$ has two very dipolar bonds, and a significant quadrupol moment. If one were to extend the nomenclature, one would say the molecule is quadrupolar. However, this may lead to complications down the line.

On the other hand, as I have written on the linked question, toluene is often considered as an unpolar/non-polar solvent, which is not really true considering it has a small dipole moment.

There are a couple of things one can predict with the concept of polarity, and fortunately, the more complex the molecules become, the better the approximation becomes. It is small highly symmetric molecules, which brake these approximations.