What is an anhydride salt?

An anhydride salt is a compound that is derived from the condensation of two or more acidic molecules, with the elimination of water. They can also be defined as salts of oxoacids whose conjugate base is an oxide ion, and have the general formula M2On, where M is a metal cation and n is the number of oxygen atoms in the salt.

In other words, anhydride salts are salts formed by the reaction between a basic oxide and an acidic oxide, with the evolution of water. The resulting salt contains the metal cation from the basic oxide and the non-metal anion (typically oxide) from the acidic oxide.

An example of an anhydride salt is sodium sulfate (Na2SO4), which is formed by the reaction between sodium oxide (Na2O) and sulfur trioxide (SO3):

Na2O + SO3 → Na2SO4 + H2O

Anhydride salts can also be formed by the reaction of a metal oxide with a mineral acid, such as:

CaO + 2HCl → CaCl2 + H2O

Anhydride salts are commonly used in the production of glass, ceramics, and other materials. They are also used as desiccants and as catalysts in various chemical reactions.