Thanks,
Im just going to outline what i think about equilibrium:
Kc can give you an idea about the extent of a reaction:
If Kc<<1 equilibrium position lies to the left
if Kc is around 1 equilibrium position is near centre
If Kc is>>1 equilibrium position lies to the right - To say this is to say the amount of product is much greater than the amount of reactant at equilibrium.
If you take the equilibrium
A (g) <--> B (g) + C (g)
And double the pressure the concentration of all species will double. But the top of the reaction quotient will increase by more and so its value would increase above Kc. Therefore, the position of equilibrium shifts to the left increasing A and using up B and C to restore the quotient to the value of Kc.
The equilibrium amount in mol of B and C will decrease and the equilibrium amount a A will increase until equilibrium is once again established. Kc doesn't change but equilibrium has been shifted to the left.
now if you had
A <--> B
And you increase the concentration of A (by adding more) The reaction quotient for the reaction would decrease to a value lower than Kc. Therefore, the equilibrium position would shift to the right so the quotient once again equals Kc. when it does the position of equilibrium will lie in its original position. If these were gases after a change in pressure the quotient would remain the same as Kc.
If you had
A + B<---> C
and you increase the concentration of A (by adding more) The quotient will have a lower value than Kc. The equilibrium will shift to the right to produce more C and use up A and B. the quotient will once again be the same as Kc.
Has equilibrium shifted:
If 1 mol of A, B and C was in 1 dm3 (at equilibrium), then Kc = 1 / 1x1 Adding 1 mol of B -> 1 / 1x2 so not Kc B + A -> C is favoured until... [A] = 0.732
= 1.732 [C] = 1.268
The net increase in moles is the same on both sides so unsure...
And Lastly (sorry for the length),
http://pmt.physicsandmathstutor.com/download/Chemistry/A-level/Past-Papers/OCR-Old/Unit-5/June%202012%20QP%20-%20Unit%205%20OCR%20Chemistry%20A-level.pdfQuestion 2bii) Obviously increasing the temperature will shift equilibrium to the left and increasing the pressure would shift equilibrium to the right. Now im just checking you can look at this two ways. Firstly, as they have not added anything like in my previous examples which makes it dodgy and just changed temp and pressure you can see that when the system is in equilibrium after these changes The position may be to the left, in the original position (if they cancel each other) or to the right. Secondly, you could also look directly after the changes have been made to see if the position has shifted in one direction or the other and therefore would eventually, when at equilibrium be shifted to the left or right.
And can you just confirm that a shift in equilibrium does not necessarily mean a change in the position permanently as in example A<-->B. and that shifting equilibrium means one of either the forward reaction or backwards reaction is favoured.
Thank you for your time