[cadmium07]

I have three (unrelated) questions:

Consider the following equilibrium equation:  CaCO3 (s) <---> CaO(s) + CO2 (g)

The equilibrium constant should be: K = [CO2]
(considering the fact that solids are generally not included)

On the other hand, equilibrium constants do not change with changing concentrations. So altering [CO2] should have no effect on K. Yet as we can see mathematically, this does not make much sense: surely if [CO2] changes, so does K? So what exactly is the flaw in this line of reasoning?


A second question:

Suppose a reaction is first order in [X] and first order in [Y]. Hence, the reaction is second order overall. So how exactly does the concentration of, say, [X] change over time?
Second order or first order?

One more (totally unrelated) question:

Compounds like cadmium chloride have a layer structure, where anions lie closely to other anions. Yet somehow this kind of compound is quite stable and it has quite a high boiling point as well (960 °C). My textbook says Van der Waals-forces keep these anions together (without any further explanation), but I can't see it happening: isn't the negativity generally located between the cations and the anions? How can Van der Waals-forces arise (and are we talking about London dispersion forces or other VDW-forces)?