Ian Stirling wrote:

Aidan Karley lid wrote:
In article
, D.M.
Procida wrote:
Why am I left with a solid and a liquid, not just some dissolved calcium
chloride?

Calcium chloride will absorb copious water from the atmosphere. The
resulting nearly neutral solution of CaCl2 will pick up small amounts of
CO2 from the atmosphere, which will produce a precipitate of calcium
carbonate. That'll be your solid residue.

If this was true, the calcium has to go out of solution too, as half of
the CaCO2.
For each molecule of CaCO2 that's produced, you've got to have an atom
of Chlorine that's released into the air (after the solution is
saturated by chlorine)

Ian,

you need to brush up a little on your chemistry, I'm afraid.

1) Calcium Carbonate is CaCO3
2) CaCO3 is ionic, so talking about 'molecules' of CaCO3 is not correct
3) Chlorine gas is molecular - Cl2. It won't be monatomic in air in
normal conditions
4) The reaction equation implied by your statements is not CaCl2 + CO2
= CaCO2 + Cl2

Calcium Chloride is hygroscopic, such that it will absorb water from
normal atmospheres to the extent of dissolving itself - and the the
solution produced continues to absorb water. In solution it will be
ionic. Ths is actually an equilibrium process - at some point the
solution will be dilute enough to not absorb any more water from the
atmosphere.

Carbon Dioxide also dissolves in water producing 'carbonic acid' -
another equilibrium process whereby there will also be carbonate and
hygrogen carbonate ions in solution. There is also another equilibrium
process between solid calcium carbonate and calcium carbonate in
solution (as a mixture of the carbonate and hydrogen carbonate).

One thing is certain, though - chlorine gas is not evolved by the
solution.

To a certain extent, all chemical reactions can be regarded as
equilibrium reactions. However, with most of them, the equilibrium lies
so far over to one side (so to speak) that it is a useful shorthand to
say that reactants are transformed into products.

Sid