Acids can be classified in two ways: first, according to the presence of oxygen-free elements, they can be divided into anaerobic acids and oxyacid. Anaerobic acids, which contain no oxygen, are named as "hydrogen acid". For example, HCl hydrochloric acid, oxyacid, which contains oxygen, are named as "an acid" with the name of the third element except hydrogen and oxygen. For example, H2SO4-- sulfuric acid. Second, according to the number of hydrogen ions generated by ionization of acid molecules: For example, HCl and HNO3 binary acids: one acid molecule ionizes two H+; for example, H2SO4 and H2CO3 ternary acids: one acid molecule ionizes three H+; for example, there are many kinds of H3PO4 salts: 1. Oxyacid salts refer to salts corresponding to oxyacids, such as Na2SO4 corresponding to H2SO4. Also, for example, Na3PO4. Anaerobic acid salt refers to the salt corresponding to anaerobic acid, such as Na2S corresponding to H2S. There is also NaCl. 2. Normal salt: the product of complete neutralization of acid and alkali. For example: NaCL acid salt: salt containing hydrogen ions in cations. For example: NAHSO4 basic salt: salt containing hydroxyl ion in anion. For example: Cu2(OH)2CO3 double salt: an isomorphic compound composed of two or more simple salts, called double salt. Double salt is also called heavy salt. The double salt contains some ions with similar size and suitable for the same crystal lattice, such as alum (potassium aluminum sulfate) kal (SO4) 212h2o mixed salt, which means that a metal ion can be divided into soluble bases (all are strong bases except TiOH). And insoluble alkali (both weak alkali), but there is also a new theory that all the protons in the reaction are alkali which helps to empty the digestive tract-not only whether it is Mg(OH)2, because MgSO4 is a laxative, and it is not clear that it is used for hydrolysis-NaOH and washing glasses or glasses. However, strong alkali must react with SiO2 _ 2. Ammonia monohydrate (weak alkali NH3.H2O), an agricultural alkali used for chemical fertilizer or medical use, is a salt composed of Ca (OH) _ 2 slaked lime and various acid ions as a building material. Such as calcium nitrate chloride Ca(NO3)Cl