In the theory of acid-base ionization, alkali refers to a substance in which all anions ionized in aqueous solution are OH-; In acid-base proton theory, alkali refers to a substance that can accept protons; In the theory of acid-base electrons, alkali refers to the electron donor.
Industrial alkali: industrial soda ash (sodium carbonate Na? CO? ), industrial caustic soda (sodium hydroxide NaOH), industrial heavy alkali (NaHCO? ）。 The purity of industrial alkali and the content of impurities (which may contain heavy metals) can meet the general industrial use, and the process is relatively simple, which can be used for large-scale industrial production and is harmful to human body.
Edible alkali: edible soda ash (sodium carbonate Na? CO? , the molecular formula is the same, but there is no impurity of industrial soda ash) and edible baking soda (sodium bicarbonate NaHCO? )。
Extended data:
Alkali can react with acid to produce salt and water (this kind of reaction is usually called neutralization reaction, which releases a lot of heat △H=57.3KJ/mol).
For example, hydrated lime (calcium hydroxide) is commonly used in industry to neutralize wastewater containing too much sulfuric acid.
Ca(OH)? +H? SO? =CaSO? +2H? O
Usually, sodium hydroxide aqueous solution is used as hydrolysis agent, and the general reaction formula is as follows:
R-X+NaOH─→R-OH+NaX
Ar-X+2NaOH─→Ar-ONa+NaX+H? O
In the formula, R, Ar and X represent alkyl, aryl and halogen respectively. Halogens in aliphatic chains are generally active and can be hydrolyzed under mild conditions, such as making benzyl alcohol from benzyl chloride; When the halogen on the aromatic ring is activated by ortho-or para-nitro groups, hydrolysis is easier, such as preparing sodium p-nitrophenol from p-nitrochlorobenzene.
Soap is made by reacting animal fatty acids with alkali (called "saponification reaction");
RCOOH+NaOH------RCOONa+H? O
Baidu Encyclopedia-Alkali