1, acid-base dissociation equilibrium, university inorganic chemistry acid-base dissociation equilibrium, when some ions meet to form weak acid and weak base salt, anion and cation mutually promote hydrolysis, and the equilibrium moves to the hydrolysis direction and hydrolysis is completed, so that the ion concentration in the solution decreases rapidly.
2. Precipitation-dissolution balance: At a certain temperature, there is a balance of dissolution and crystallization between insoluble electrolyte crystals and ions dissolved in the solution, which is called multi-ion balance, also known as precipitation-dissolution balance.
3. Redox equilibrium is to consider the progress of reaction from the potential of redox electrode.
4. Complexation and dissociation equilibrium. There are various natural or synthetic ligands in soil, which can form complexes or chelates with different stability with heavy metal ions.