Explain the relationship between forward and backward reactions in equilibrium, and predict how changing the amount of a reactant (creating a tension) will affect that relationship.

1- Equilibrium determines the rate of reactants and products at the same time.

General expression for equilibrium:

                                     Reactants⇌ Products

2- At equilibrium, all the reactants and products are constant.

3- At equilibrium forward and reverse reaction does not stop, in fact, it continues at all times.

4- When the concentrations of reactants and products become equal dynamic equilibrium is obtained.

For example:

         A + B ⇌ C + D

In this reaction, if the concentration of reactant  A has increased the equilibrium will shift to the right to form more products.

If the concentration of reactant A has decreased the equilibrium will shift to the left in the backward direction to form reactants.