A salt metathesis reaction is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding affiliations.[1] This reaction is represented by the general scheme:
For more details about displacement reactions, go to single displacement reaction
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Typical examples are the reactions between oxysalts and binary compounds such as salts, hydrohalic acids and metal hydroxides:
Another classical example are the reactions between oxysalts in solution:
The bond between the reacting species can be either ionic or covalent. Classically, these reactions result in the precipitation of one product.
In older literature, the term double decomposition is frequently encountered. The term double decomposition is more specifically used when at least one of the substances does not dissolve in the solvent, as the ligand or ion exchange takes place in the solid state of the reactant. For example:
- AX(aq) + BY(s) → AY(aq) + BX(s).
Neutralization reaction
A neutralization reaction is a type of double replacement reaction. A neutralization reaction occurs when an acid reacts with an equal amount of a base. This reaction usually produces a salt. One example, hydrochloric acid reacts with disodium iron tetracarbonyl to produce the iron dihydride:
- 2 HCl + Na2Fe(CO)4 → 2 NaCl + H2Fe(CO)4
Reaction between an acid and a carbonate or bicarbonate salt yields carbonic acid, which spontaneously decomposes into carbon dioxide and water. The release of carbon dioxide gas from the reaction mixture drives the reaction to completion. For example, a common, science-fair "volcano" reaction involves the reaction of hydrochloric acid with sodium bicarbonate:
- 2 HCl + Na2CO3 → H2CO3 + 2 NaCl
- H2CO3 → H2O + CO2
In contrast to salt metathesis reactions, which are driven by the precipitation of solid salts, are salt-free reductions, which are driven by formation of silyl halides, Salt-free metathesis reactions proceed homogeneously.[5]