Question

How does an anhydride differ from an acid?

Answer 1

acid is formed when water is added to an anhydride

Explanation:

when you add water into anhydrides, the relative acids are formed. for example, take `SO_3`, when you add water it forms `H_2SO_4` which is the hydride or simply the acid. notice that the oxidation state has not changed even though the anhydride has turned into it's acid.

some more examples for addition of water into anhydrides

`SO_2 + H_2O rarr H_2SO_3`
`CO_2 + H_2O rarr H_2CO_3`
`N_2O_5 + H_2O rarr HNO_3`
`P_2O_5 + H_2O rarr H_3PO_4`

so basically anhydride is the state without water, while the acid is the state with water in it.