Question

How to determine anhydrides of acids and bases?

Answer 1

Anhydrides are functional groups which are basically the derivatives of either acids or bases.

Explanation:

Anhydrides are functional groups which are basically the derivatives of either acids or bases. Acid anhydrides will have R-COO-CO-R' pattern where R and R' are alkyl groups. While basic anhydrides will not have such a pattern of atomic or molecular connections.

Answer 2

If an anhydride produces acid/s on addition of water to it,then the anhydride will be anhydride of acid/s. These are generally oxides of nonmetal

For example

1 .`SO_2+H_2O->H_2SO_3`

Here `SO_2` forms `H_2SO_3` when reacted with water . So `SO_2` is anhydride of `H_2SO_3`

2 .`(CH_3CO)_2O+H_2O->2CH_3COOH`

Here `(CH_3CO)_2O` forms `CH_3COOH` when reacted with water . So `(CH_3CO)_2O` is anhydride of `CH_3COOH`

3 .`2NO_2+H_2O->HNO_2+HNO_3`

Here `NO_2` forms `HNO_3 and HNO_2` when reacted with water . So `NO_2` is mixed anhydride of `HNO_3 and HNO_2`

If an anhydride produces base on addition of water to it,then the anhydride will be anhydride of base. These are generally oxides of metal. (Exception: Some higher valent metallic oxides can form acids when treated with water. They should be treated as anhydride of acid)

Example

`CaO+H_2O->Ca(OH)_2`

Here `CaO` forms `Ca(OH)_2` when reacted with water . So `CaO` is anhydride of `Ca(OH)_2`