Basic salt

[jiǎn shì yán]

chemical compound

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Chemical salt It is divided into single salt and Compound salt , single salt is Orthosalt 、 Acid salt , alkaline salt, combined salt is Double salt and Complex salt 。 Basic salt is defined as ionization Removal of anions generated at Acid radical ion Besides Hydroxyl ion , cation is metal ion (or NH four + ）Salt.

Chinese name: Basic salt
Foreign name: Basic salt
Main signs: Ionizable hydroxyl ion in anion containing water

Salt classification: Single salt and Compound salt
Single salt classification: Orthosalt 、 Acid salt 、 Basic salt
Classification of combined salts: Double salt and Complex salt

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Introduction to basic salt

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Alkali salt contains hydroxyl Or oxy salt. General composition: metal+OH - + Acid radical

When naming, hydroxyl is represented by "hydroxyl", oxygen is represented by "oxidation", and its number is represented by one, two, and three. "one" can be omitted, such as Iodate Copper hydroxide Cu (OH) IO three Antimony dioxide sulfate (SbO) two SO four Or antimony oxysulfate; Malachite Cu, a natural mineral two (OH) two CO three 、 hydroxyapatite Ca five (PO four ) three ·(OH), which are basic salts containing hydroxyl; Antimony dioxide sulfate (SbO) two SO four It is a basic salt containing oxygen group.

Except for metal ions and Acid radical ion In addition, there are 1 or n hydroxyl Or oxy. Alkali salt can also be considered as Hydroxyl radical The product not completely neutralized by acid. Hydroxyl salts can be regarded as metal ions and OH - And other anions Double salt , e.g. Mg (OH) Cl can be regarded as Mg 2+ And OH - 、Cl - It is composed of double salt. Oxyl salt is also called Oxide salt , can be regarded as metal ions and O 2- And other anions, such as SbOCl, can be regarded as Sb 3+ And O 2- 、Cl - It is composed of double salt.^[1]

Physical and chemical properties

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Mostly alkaline solubility Not much. However, the composition of some basic salts varies with different preparation conditions. For example, in a closed pipe copper sulphate Solution and calcium carbonate Cu (OH) obtained by heating the mixture to 423 ～ 443K (i.e. about 150 ℃) two ·CuCO 3， Cu (OH) is generated at a lower temperature two ·2CuCO three 。

When acid reacts with base Hydroxyl ion Some are neutralized, and the salt generated is alkaline salt. Monobasic base It cannot form basic salt, Binary base Or polyalkaline may form alkaline salt. The composition and properties of basic salts are complex and diverse. Basic copper carbonate Cu2(OH)2CO3 and Basic magnesium chloride Mg(OH)Cl Hydroxyapatite Ca5 (OH) (PO4) 3 All of them belong to basic salts.

Conditions and laws

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1. Hydrolysis reaction of salts of low valent metal ions of group Ⅳ A and Ⅴ A and salts of group Ⅱ B, for example:

SbCl three +H two O→SbOCl↓+2HCl

ZnCl two +H two O→Zn(OH)Cl+HCl

When such salt solution is prepared in the laboratory, corresponding acid must be added to inhibit hydrolysis. For example, the most common hydrate of mercuric nitrate is Hg (NO three ) two ·H two O， It is a mercury salt easily soluble in water. Since it is strongly hydrolyzed in water to form insoluble alkaline salt, it should be dissolved in dilute nitric acid solution when preparing solution.^[2]

2. High temperature hydrolysis reaction of chloride containing crystal water, for example:

2CuCl two ·2H two O→Cu(OH) two ·CuCl two +2HCl↑+2H two O

ZnCl two ·H two O→Zn(OH)Cl+HCl

Preparation of anhydrous CuCl from aqueous salt in industry two 、ZnCl two It must be heated and dehydrated in the hydrogen chloride gas stream to prevent hydrolysis.

3、 Amphoteric oxide React with other substances, such as:

2ZnO+H two O+CO two →Zn two (OH) two CO three

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The acid salt is a cationic metal removal ion [or NH four + (It has the property of metal ions)] In addition to hydrogen ions, anions are salts of acid radical ions. The basic salt is the anion generated during ionization. In addition to the acid radical ion Hydroxyl ion , cation is metal ion (or NH four + ）Salt.

Judge salt NaHCO three And Na two HPO four Whether it is normal salt, acid salt or alkali salt, just look at NaHCO three And Na two HPO four Whether it can continue to react with a strong base (such as NaOH) or a strong acid (such as HCl). If it can, see whether the reaction only generates new salt and water. Due to NaHCO three When reacting with NaOH, only new salt Na can be generated two CO three And H two O； Similarly, Na two HPO four Reaction with NaOH can only generate new salt Na three PO four And H two O。 By definition, due to NaHCO three And Na two HPO four When reacting with alkali, only new salt and water are generated, and no other new substances are generated, so NaHCO three And Na two HPO four All are acid salts. Although NaHCO three And Na two HPO four All can react with HCl, except that they can generate new salt NaCl, in which NaHCO three CO is also generated two And H two O， And Na two HPO four Not only didn't I get H two O， Instead, salt NaH is generated two PO four Or acid H three PO four , so it is not an alkaline salt by definition. Due to NaHCO three And Na two HPO four They can continue to react with strong base NaOH, and only generate salt and water, so they are not normal salts, so NaHCO three And Na two HPO four All are acid salts.^[3]

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