Thanks Jake, just one more q, Why is it when pressure is increased the concentrations of everything increases instantaneously but then equilibrium shifts to side with fewer moles of gases. Also does this instant increase happen with any of the other variables (e.g. temperature or concentration). What i mean is, if the temperature is increased, does everything else increase suddenly then equilibrium shifts right or left (depending if exo/endo) and everything decreases or increases according to this new equilibrium position?
We had this discussion on pressure already.
The concentration of the solids are constant, only (aq) and (g) are in the equilibrium expressions. You can exclude pure solids and pure liquids from the equilibrium expressions.
What I thought. I remember being taught this but it was a blur.When you add more moles of solid, you add the same amount of volume of the solid to counteract a potential increase in concentration. Given C=n/V, if n and V go up in the exact same proportion, the concentration is not affected.
Note that it is the CONCENTRATION of the substance which shifts the equilibrium, not the actual quantity (moles)
Temperature is different. Temperature depends on your enthalpy change value, that is, your value for ΔH. The value for ΔH has nothing to do with the state your substances are in, be it solid, liquid or gaseous.
If you mean the actual concentrations, which are best depicted on a graph, then
no, only changes in concentrations spike the graph up. This is because a change in temperature is nothing but a
change in temperature - we are not introducing or extracting a substance relative to the volume of the vessel. Pressure or increases in concentration disturbs the ratio of substances (moles) to the volume of the vessel (volume, and note C=n/V), whereas temperature does not.
Note that the more gradual changes later are
just a consequence of Le Chatelier's principle. The spikes are when we suddenly change concentrations in a matter of a second, whereas what comes next is the system trying to shift it's equilibrium to counter the change. (Once again - temperature does NOT forcibly disturb what's in there immediately, as opposed to e.g. taking out 2L of hydrogen.)