Any bond or inter-molecular attraction can be formed and broken. These two processes are in a dynamic competition, sensitive to initial conditions and external perturbations.
Section 1: Chemical equilibrium
Equilibrium is a dynamic state that is reached as the rate of the forward reaction equals the rate of the reverse reaction. Equilibrium is a stoichiometric point that is reached as reactants are converted to products. When at equilibrium the ratios of the reactants to products does not change and the value of the ratio is defined as the equilibrium constant, K.
Section 2: Disturbing equilibrium
At equilibrium, the rates of the forward and reverse reactions are equal. Any stress that would affect the rates disproportionately will cause a shift away from equilibrium and give the reaction a net direction. The system will proceed to reestablish equilibrium under the new conditions.
Section 3: Acid-Base and Solubility Equilibrium
Chemical equilibrium plays an important role in acid-base chemistry as well as solubility. In acid-base chemistry the gain/loss of a proton is a reversible process that reaches equilibrium quickly. In terms of solubility the dissociation of a solid solvent is also a reversible process that reaches equilibrium quickly.
Section 4: Equilibrium Constant Relationships
The equilibrium constant can be related to Gibbs Energy and temperature.