Definition and Classification of Salts

A salt is made up of 2 parts: A positive cation from a METAL/AMMONIUM and a negative anion from an ACID

The Table given below classifies all salts into SOLUBLE or INSOLUBLE salts.

Classification of a salt is VERY important. It will determine the method you will choose when preparing a salt. Follow the following flowchart to determine which method to use to prepare the salt you have in mind.

Salt Preparation - Titration

Concept: Reacting 2 solutions in EXACT amounts to produce a pure salt solution. (How to know this? Will this contaminate the salt solution? How do you solve this problem?)

Choosing the reagents to use: An acid is usually reacted with another soluble compound.

The following video shows the titration reaction.

Salt Preparation - Precipitation Method

Concept: add 2 solutions which each contain one ion of the compound to be formed, together. When the ions come into contact with each other, the precipitate is formed instantaneously.

Choosing the reagents to use: ensure both reagents chosen are soluble.

Salt Preparation - Excess Insoluble Reagent Method

Concept and Methodology: In this method, one reagent is soluble, but the other reagent is insoluble. So to ensure that all of the soluble reagent is used up, EXCESS of the solid reagent must be added, and then removed to obtain a pure salt solution.

Choosing Reagents: One reagent is soluble, while the other is not.

Case Study 1 - Oceans