Equilibrium constant vs Equilibrium concentration

[kimtywong]

hey guys, mind telling me the difference between Equilibrium constant and equilibrium concentration?

In Smartstudy...
 QS)  Nitrogen Monoxide gas reacts with steam according to the following equation.
                4NO(g) + 6H2O(l)      <--> 4NH3(g) + 5O2(g)     endo
        If the volume of the reaction vessel is decreased, will the equilibrium CONCENTRATION of nitrogen monoxide (NO) increase, decrease, or remain unchanged? Explain your choice.

I thought it never changes hence i stated that it remains unchanged, but apparently, the solution said that the equilibrium CONCNETRATION increases!    So there must be a difference between equilibrium constant and equilibrium concentration.

help!!

[/0]

Equilibrium constant, the big , is only changed by temperature.



, , and are the equillibrium concentrations of , , , and respectively.

If the volume of the reaction vessel is decreased, the equilibrium concentration of ALL species increases.

There are less particles on the RHS, so you will get a net forward reaction by LCP to partially offset the increase in pressure, but since it is only a partial offset, the net change in is that it increases.

[kimtywong]

ohhhhh, so when it says... equilibrium concentration of X, what it saying is the concentration of X at equilibrium? not the fraction thingy?

[/0]

yep

[kimtywong]

OH MY GOODNESS. i never knew that. lightblub moment!! thanks /0!