Preparation of a soluble salt

Question 1

How can titration be used to prepare a soluble salt?

Answer 1

Titration is used to determine the volume of acid needed to neutralise a known volume of alkali. (or vise versa). Once the volumes of acid and alkali have been noted the reaction can be repeated without the indicator to produce an uncontaminated salt solution. The solution can then be evaporated to dryness. This method is usually used for preparation of group 1 and ammonium salts.

Question 2

How can the use of insoluble metal oxides/ carbonates prepare a soluble salt?

Answer 2

Excess of an insoluble metal oxide/ carbonate is added to the appropriate acid until no more reacts. For a carbonate it is easy to tell when the acid has all reacted because the fizzing would stop- no more gas is produced.
The excess base is removed by filtration.
The soluble salt is obtained by evaporation of the filtrate by heating it in an evaporating basin.

Question 3

What is residue?

Answer 3

The residue is the mixture filtered to remove the excess product.