[Foobarz]

Ok, so here's something I'm not understanding. How come for something A(s) B(g), adding more A doesn't shift the equilibrium? That doesn't make any sense, since wouldn't the extra reactant be used up to form the gaseous product?

[Foobarz]

All right so specifically its this question:

2NaHCO₃(s) Na₂CO₃(s)+H₂O(g)+CO₂(g)

So the K_c is determined by [CO₂][H₂O]. Lets say volume is 1 L and number of moles for both products is 1. All other factors are constant. So concentration of both is 1M. So, what happens if I only put in 1 mol of NaHCO₃? That's only enough to produce 0.5 mol, and 0.5 mol/L is only 0.5 M. Yet I thought it was the equilibrium CONSTANT

[Borek]

Have you learned about solubility product?

This is in a way similar. If partial pressures of gases are high enough you will observe solid bicarbonate (that is, assuming there was a carbonate present). If the pressures are too low there will be no bicarbonate. However, once the bicarbonate is present, it doesn't matter how much there is - product of concentrations (or partial pressures of gases) will be constant.