WAEC - Chemistry (1997 - No. 13)

Which of the following is a general method of preparing acids?

Direct combination of constituent elements

Reaction between a base and an amphoteric oxide

Double decomposition involving a salt solution

Reaction between an anhydride and water

Dissolution of hydroxides followed by neutralization

The correct answer is D - Reaction between an anhydride and water.

This is a general method of preparing acids, where an anhydride (a compound that lacks water) reacts with water to form an acid. For example:

SO\(_3\) + H\(_2\)O → H\(_2\)SO\(_4\)

CO\(_2\) + H\(_2\)O → H\(_2\)CO\(_3\)

This method is commonly used to prepare various types of acids, including inorganic acids like sulfuric acid, nitric acid, and phosphoric acid.