Methods of preparing soluble salts

Titration Titration is used to prepare a soluble salt (such as sodium chloride) from a soluble base (such as sodium hydroxide).

Titration is specifically used to prepare soluble salts of group 1 metals and ammonium salts.

 

Method:

1.    Fill a burette up to its zero mark with dilute HCl

2.    In a conical flask, pour a specific volume of NaOH

3.    Add few drops of phenolphthalein to the conical flask containing NaOH

4.    Add some HCl from the burette to the NaOH till the purple-pink colour of phenolphthalein changes to colourless.

5.    Record the volume of acid required to neutralize the specific volume of alkali.

 

Neutralization (of a base with an acid) This method is used to produce soluble salts of most other metals.

 

Method:

1.    An excess of the base is added to the acid

2.    The mixture is filtered to remove the excess volume of base

3.    The filtrate is extracted and is heated until the point of crystallization has been achieved.

4.    The heat is turned off and left to crystallise.

 

Reacting a metal with an acid This method can be used to produce soluble salts of less reactive metals such as zinc, aluminium, magnesium etc.

 

Method:

The method is the same as mentioned above, except that the reaction is redox (and not neutralization).

 

Methods of preparing insoluble salts

Insoluble compounds are:

Compound Exceptions
All carbonates Group 1metal carbonates

Ammonium carbonate

All hydroxides Group 1 metal hydroxides

Calcium hydroxide

Strontium hydroxide

Barium hydroxide

Barium sulphates

Calcium sulphates

Lead sulphates

All sulphates
Chlorides, bromides and iodides of silver and lead

Example: How to prepare the insoluble salt barium sulphate?

To prepare the insoluble salt barium sulphate, two solutions need to be mixed:

  1. A solution containing a soluble barium salt
  2. A solution containing a soluble sulphate

The precipitate needs to be obtained (from mixing both solutions)

The precipitate needs to be washed with distilled water

And finally it needs to be dried, producing the insoluble salt- barium sulphate.

 

 

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