Note When the electrolyte reaches ionization equilibrium, the percentage of ionized electrolyte molecules in the solution to the total number of original molecules (including ionized and non-ionized) is called ionization degree. It is usually expressed as α.

For weak electrolyte, the relative strength of weak electrolyte can be measured and compared with the ionization degree data of electrolyte at the same temperature and concentration. Generally, the ionization degree is 25℃. The ionization degree and ionization constant Ki of weak electrolyte can be converted by the following formula:

Where c is the concentration of the solution. If the electrolyte is weak and the ionization degree α is small, the denominator is 1α≈ 1. The degree of ionization increases with the dilution of the solution. This change law is called dilution law, which is not suitable for strong electrolyte; For polybasic weak acids or polybasic weak bases, the dilution law only applies to their first-order ionization. Strong electrolyte is completely ionized in dilute solution (α 100%). However, due to the large ion concentration and small ion spacing, the free movement of ions is limited by strong electrostatic action. In addition, like charges repel and opposite charges attract, so there are many negative ions around the positive ions, and there are also many positive ions around the negative ions, which makes them move to the electrode slower than those without "concern" when energized, so the actually measured ionization degree is not 100%. This ionization degree less than 100% is called the apparent ionization degree of strong electrolyte. Can not truly reflect the ionization degree of strong electrolyte in solution.