changing the amount of a substance that participates in an equilibrium
For example: adding Hydrogen ions causes a dislocation of the equilibrium, that will take care that (part of) the extra Hydrogen ions will go away again, by stimulating the forward reaction.
This continues until a new equilibrium is reached.
In the beaker is NH3(aq) (basic environment) with some drops of the indicator methyl red,
of which the abbreviated formula is: HIn
Than in the solution the following equilibrium will occur:
HIn H++ In-
The presence of a base (that absorbs H+) means a dislocation of the equilibrium to the right.
the yellow color dominates.
Now you add a bit of HCl(aq), the basic environment changes to a less basic or more aced env.
The acid wil donate H+, so:
the equilibrium: HIn H++ In-
dislocates to left and the red color will dominate.
Now again we add some base:
Nu gaan we weer base toevoegen: (NH3(aq)), the color changes again to yellow
so the same equilibrium dislocated again to the right:
Doing this can be repeated endless.
Every time the equilibrium will dislocate to the right of to the left.
The overall situation in the beaker does only change a very littlebit.
There is only a small dislocation of the equilibrium to one of the other side, dependent on the environment.