Consider the following system at equilibrium:

D (aq) + E (aq) F (aq)

Classify each of the following actions by whether it causes a leftward shift, a rightward shift, or no shift in the direction of the net reaction.

Increase D

Increase E

Increase F

Decrease D

Decrease E

Decrease F

Triple D and reduce E to one third

Triple both E and F

Increase D ⇒ rightward shift

Increase E ⇒ rightward shift

Increase F ⇒ leftward shift

Decrease D ⇒ leftward shift

Decrease E ⇒ leftward shift

Decrease F ⇒ rightward shift

Triple D and reduce E to one third ⇒ no shift

Triple both E and F ⇒ no shift

Explanation:

Changes in the concentrations of reactants y products affect to the equilibrium. In this case, D and E are reactants and F is the product.

When a change in the factors affecting equilibrium occur, the system will react in order to counteract the change imposed.

If a increase of reactant occur, the system will tend to produce more products (rightward shift). For example: increase D, increase E. In contraposition, if a decrease of reactant occur, the system will produce more reactants (leftward shift). For example: decrease D, decrease E. If a increase of product occur, the system will tend to produce more reactants (leftward shift). For example: increase F. In contraposition, if a decrease of product occur, the system will produce more products (rightward shift). For example: decrease F. If we change both reactants and products concentration in the same amount, the net change is zero, so there is not shift. For example: Triple D and reduce E to one third (D x 3 and E/3, there is not change in the total amount of reactants); Triple both E and F (E x 3 and F x 3, the net change is zero).