# Chemistry: Equilibrium

Hello there. I'm having trouble understanding equilibrium. Especially understanding if the reactions go foward or reverse when there is a change in tempertature, concentration, pressure/volume etc. For example:

In a solution of copper (II) chloride, the following equilibrium exists.

$$CuCl_4^{2-}_{(aq)} + 4H_2O_{(l)} \rightleftharpoons Cu(H_2O)_4^{2+}_{(aq)} + 4Cl^{-}_{(aq)}$$

For the following stresses put on the equilirbrium, predict the shift in the equilibrium.

1) Hydrochloric acid is added
2) Silver nitrate is added.

1) Would this be a reverse reaction since the acid dissociates into $$HCl_{(aq)} \rightarrow H^{+}_{(aq)} + Cl^{-}_{(aq)}$$? So the concentration of Cl will be increased and it will shift to the left?

2)I think it's a reverse reaction but I'm not sure. Why would it be a reverse reaction (or foward if I'm wrong)? Thanks for the help.

## Answers and Replies

erik05 said:
Hello there. I'm having trouble understanding equilibrium. Especially understanding if the reactions go foward or reverse when there is a change in tempertature, concentration, pressure/volume etc. For example:

In a solution of copper (II) chloride, the following equilibrium exists.

$$CuCl_4^{2-}_{(aq)} + 4H_2O_{(l)} \rightleftharpoons Cu(H_2O)_4^{2+}_{(aq)} + 4Cl^{-}_{(aq)}$$

For the following stresses put on the equilirbrium, predict the shift in the equilibrium.

1) Hydrochloric acid is added
2) Silver nitrate is added.

1) Would this be a reverse reaction since the acid dissociates into $$HCl_{(aq)} \rightarrow H^{+}_{(aq)} + Cl^{-}_{(aq)}$$? So the concentration of Cl will be increased and it will shift to the left?
Yes exactly,

2)I think it's a reverse reaction but I'm not sure. Why would it be a reverse reaction (or foward if I'm wrong)? Thanks for the help.
Silver nitrate is soluble in water, but silver chloride isn't. So adding silver nitrate is like taking away chloride ions from solution...