Amphoteric oxides: poorly soluble in water, but soluble in strong acids (such as HCl) and strong bases (such as NaOH).

Amphoteric oxides include BeO, Al2O3, Cr2O3, ZnO, etc.

The "amphitrope" of amphoteric oxides can also be understood as being able to express the properties of both acidic oxides and alkaline oxides. Although the acid salt of a weak acid or a weak base salt of a weak acid can react with both an acid and a base, it cannot produce "salt and water" and is therefore not an amphoteric compound. The "ambidexterity" of amino acids and proteins means that their structures have both basic genes that can react with acids and acidic groups that can react with alkali. Sometimes we also call substances that can exhibit both oxidizing and reducing properties "amphiphilic" substances.

They cannot react with acids or bases to form salts and water. This Oxides are called non-salt-forming oxides. For example, H2O, NO, CO, N2O, NO2, N2O4, TeO, ClO2, I2O4, and MnO2 are non-salt-forming oxides.

Carbon monoxide can react with sodium hydroxide to form the sodium salt of formic acid. However, no water is formed when salt is formed, so carbon monoxide is still a non-salt-forming oxide.

Manganese dioxide and nitrogen dioxide are non-salt-forming oxides, lt;/CQgt; because the valence of the oxygen-containing acids of manganese and nitrogen corresponding to these two elements is not 4.

The corresponding oxide of permanganate is manganese heptaoxide rather than manganese dioxide.

The corresponding oxide of nitrate is dinitrogen pentoxide rather than nitrogen dioxide.

Normal salt definition: contains neither ionizable hydrogen ions nor hydroxyl radicals Ionic salt.

Normal salt is the product of complete neutralization of acid and alkali, but the aqueous solution of normal salt is not necessarily neutral, such as Na2CO3 (sodium carbonate) solution is alkaline, (NH4)2SO4 (ammonium sulfate) solution Acidic.

In the salt formed by the complete neutralization of acid and base, there will be no hydrogen ions in the acid or hydroxide ions in the base, only metal cations and acid ions. Such a salt is Right salt. Reactions that generate normal salts, such as:

HCl NaOH=NaCl H2O

H2SO4 Cu(OH)2 = CuSO4 2H2O

H2SO4 2NaOH=Na2SO4 2H2O, etc.

Acid salt definition: The cations generated during ionization include hydrogen ions in addition to metal ions (or NH4), and the anions are salts of acid ions.

(1) Judgment of acidity and alkalinity of acid salt water solution:

① Acid salt whose aqueous solution is acidic

a. Acid salts of strong bases and strong acids: such as NaHSO4, completely ionized in its aqueous solution: NaHSO4=Na H SO42-, because [H]>[OH-], the solution is acidic; similarly, NaH2PO4, NaHSO3

b． Acidic salts of strong bases and weak acids: such as Ca(H2PO4)2, the aqueous solution undergoes an ionization reaction and a hydrolysis reaction at the same time. However, because the "ionization" trend is greater than the "hydrolysis" trend, the solution is acidic. In the same way, NaH2PO4 and NaHSO3 are both acidic.

② Acid salts whose aqueous solution is alkaline:

Generally acid salts of strong bases and weak acids, such as Na2HPO4 solution, because the "ionization" trend is smaller than the "hydrolysis" trend, So the solution is alkaline.

(2) Thermal stability of acid salt:

Generally, the thermal stability of normal salt is greater than that of acid salt.

Na2CO3, 2NaHCO3 Na2CO3 CO2↑ H2O

CaCO3 CaO CO2↑, Ca(HCO3)2 CaCO3 CO2↑ H2O

(3) Acid salt of weak acid , can react with both base and acid.

NaHCO3: NaHCO3 NaOH=Na2CO3 H2O

NaHCO3 HCl=NaCl CO2↑ H2O

2NaHCO3 H2SO4=Na2SO4 2CO2↑ 2H2O

( 4) Comparison of the degree of hydrolysis of acid salts and normal salts:

The hydrolysis degree of acid salts of strong bases and weak acids is smaller than the hydrolysis degree of normal salts of strong bases and weak acids. For example, NaHCO3 and Na2CO3

There is only one step in the hydrolysis of NaHCO3: HCO3- H2O H2CO3 OH-, [OH-]>[H]

Obviously, two solutions of the same concentration are alkaline: NaHCO3＜Na2CO3

In middle school, all acid salts are defined as soluble in water. If they want to precipitate, they must exceed the solubility. They do not have to be insoluble in water to precipitate

For example, when carbon dioxide is introduced into a saturated solution of sodium carbonate, sodium bicarbonate will precipitate. The equation is

Na2CO3 + CO2 H2O = 2NaHCO3 (precipitation symbol)

Reminded me from upstairs I, in fact, the high school textbooks did not mention precipitable acid salts, but it appeared in the exercises. Calcium hydrogen phosphate, Ca(HPO4)2, precipitates and is insoluble in water, so phosphorus fertilizers cannot be mixed with alkaline fertilizers. For example, when used together with ammonia and water, the calcium dihydrogen phosphate mentioned above only has a low solubility and is not insoluble in water, so it is a soluble substance.

PS: Add the solubility of sodium bicarbonate: the solubility of sodium bicarbonate is: 9.6g (20℃), 11.1g (30℃),

Basic salt definition: In addition to acid ions, the anions generated during ionization also include hydroxide ions, and the cations are salts of metal ions (or NH4).

When an acid reacts with a base, the hydroxide ions in the weak base are partially neutralized, and the salt formed is a basic salt. Monobasic bases cannot form basic salts, only dibasic or polybasic bases can form basic salts. The composition and properties of basic salts are complex and diverse. Basic copper carbonate Cu2(OH)2CO3 and basic magnesium chloride Mg(OH)Cl are all basic salts.

Basic salt

basic salt

A salt containing a hydroxyl or oxygen group. For example, the naturally occurring minerals malachite Cu(OH)2·CuCO3 and hydroxyapatite Ca5(PO4)3·(OH) are basic salts containing hydroxyl groups; antimony sulfate dioxide (SbO)2SO4 contains Basic salt of oxygen group. In addition to metal ions and acid ions, basic salts also contain 1 or n hydroxyl or oxygen groups. Basic salts can also be thought of as products in which the hydroxide radical in the base has not been completely neutralized by the acid. Hydroxy salt can be regarded as a double salt composed of metal ions, OH- and other anions. For example, Mg(OH)Cl can be regarded as a double salt composed of Mg2, OH- and Cl-. Oxygen salts, also known as oxidation salts, can be regarded as double salts composed of metal ions, O2- and other anions. For example, SbOCl can be regarded as a double salt composed of Sb3, O2- and Cl-. The composition of some basic salts can vary due to different preparation conditions. For example, Cu(OH)2·2CuCO3 is generated at a lower temperature, and Cu(OH)2·CuCO3 is generated at a higher temperature.

After explaining the definition, the difference is obvious.