Equilibrium Position

Question

So if you had the equilibrium $\ce{A <--> B}$ and you increase the concentration of A. I understand that equilibrium will shift to the right. To say this (I believe) is to say that the $\ce{A -> B}$ reaction is favoured. But when at equilibrium again will the position of equilibrium be back in its original position, as I believe the position of equilibrium to be defined as the amount of A relative to B.

If this is true, does it follow that a shift in equilibrium does not necessarily mean a permanent change in the position?

If it was a $\ce{A + B <--> C}$ equilibrium and you increase the concentration of A the equilibrium will shift to the right. How would you determine if the position had changed at equilibrium?
Thanks very much.

Answer 1

Not knowing what the chemicals in your equation are or what kind of properties they have, I can't tell you how you would measure their concentrations.

Nonetheless, given:

$$\ce{A + B <--> C}$$

If you add an additional, preferably known, quantity of A, then the concentration of B should decrease and the concentration of C should increase.

This is actually just the real meaning behind your statement that "the equilibrium will shift to the right". In this case, with two reactants, obviously more of the second one (B) must be consumed by the addition of more A in order to produce more C (shift to the right).

Again, how you would measure the concentrations of B and C depends on which compounds B and C actually represent.