First, the introduction of salt:
Chemically, salt refers to a class of compounds in which metal ions or ammonium ions are combined with acidic ions, such as calcium sulfate, copper chloride, sodium acetate, etc. Generally speaking, salt is the product of double decomposition reaction, such as sulfuric acid and sodium hydroxide to produce sodium sulfate and water, and other reactions can also produce salt, such as displacement reaction.
Salt can be divided into single salt and double salt. Single salt has normal salt, acid salt and alkaline salt, and double salt has double salt and double salt. Among them, acid salts contain hydrogen ions in addition to metal ions and acid ions, and basic salts also contain hydroxide ions in addition to metal ions and acid ions. The compound salt can be dissolved in water, and can generate the same combined salt as the original salt ion. The complex salt can produce complex ions different from the original salt when it is dissolved in water.
Usually, under standard conditions, insoluble salts will be solid, but there are exceptions, such as molten salts and ionic liquids. Soluble salt solution and molten salt are conductive, so they can be used as electrolytes. There are many different salts in cytoplasm, blood, urine and mineral water.
Second, the physical properties:
The color of salt can be pure, transparent, opaque or metallic. In most cases, the transparency or opacity of the salt surface is only related to the single crystal that constitutes the salt. When the light shines on the salt, it will be reflected by the grain boundary, and the large crystals will appear transparent, and the polycrystals together will look more like white powder.
Strong acid or strong base salt is nonvolatile and odorless. However, weak acids or weak base salts will produce different smells according to acid-base pairs. For example, acetate will taste like acetic acid, and hydrogen cyanide will taste like bitter almond. In addition, weak acid or weak base salt will volatilize and decompose, and because hydrolysis reaction and weak salt synthesis reaction are reversible, the decomposition of weak salt will be accelerated in the presence of water.
Third, the chemical properties:
Chemically, salt is a neutral (uncharged) ionic compound, which consists of cations (positively charged ions) and anions (negatively charged ions). The metal in the reaction must be more active than the metal in the salt before it can be replaced.