Making salt
The salts made in
neutralisation reactions can
be either soluble or
insoluble.
Making of salt
The method of preparing
and purifying the salt
depends on whether or not
it is soluble in water.
Naming salts
A salt is any compound formed by
the neutralisation of an acid by a base.
The name of a salt has two parts. The first
part comes from the metal, metal oxide or
metal carbonate. The second part comes
from the acid.
Naming salts
You can always work out the name of the salt by looking
at the reactants:
• nitric acid always produces salts that end in nitrate and
contain the nitrate ion, NO3-
• hydrochloric acid always produces salts that end in
chloride and contain the chloride ion, Cl-
• sulfuric acid always produces salts that end in sulfate and
contain the sulfate ion, SO42-
Naming salts
For example, if potassium oxide reacts with sulfuric acid,
the products will be potassium sulfate and water.
The table shows some more examples
Metal Acid Salt
reacts Sodium
Sodium hydroxide Hydrochloric acid to make
with chloride
reacts Copper
Copper oxide Hydrochloric acid to make
with chloride
reacts
Sodium hydroxide Sulfuric acid to make Sodium sulfate
with
reacts
Zinc oxide Sulfuric acid to make Zinc sulfate
with
Naming salts
ammonia forms ammonium salts when it
reacts with acids.
For instance, ammonia reacts
with hydrochloric acid to make ammonium
chloride.
Preparing salts
• Some salts can be extracted by mining but others need to be prepared in
the laboratory.
• There are two key ideas to consider when preparing salts:
• Is the salt being formed soluble or insoluble in water?
• Is there water of crystallisation present in the salt crystals?
Salt solubility
Preparing soluble salts
Method A: adding acid to a solid metal, base or carbonate
Example: Preparation of pure, Hydrated Copper (II) Sulphate Crystals using
Method A
Acid = Dilute Sulfuric Acid
Insoluble base = Copper (II) Oxide
Method:
• Add dilute sulfuric acid into a beaker and heat using a Bunsen burner flame
• Add copper (II) oxide (insoluble base), a little at a time to the warm dilute
sulfuric acid and stir until the copper (II) oxide is in excess (stops
disappearing)
• Filter the mixture into an evaporating basin to remove the excess copper (II)
oxide
• Leave the filtrate in a warm place to dry and crystallize
• Decant excess solution
• Blot crystals dry
Equation:
Copper (II) Oxide + Dilute Sulfuric Acid → Copper (II) Sulphate + Water
Preparing soluble salts
Method B: reacting a dilute acid and alkali
Method
• Use a pipette to measure the alkali into a conical flask and add a few
drops of indicator (phenolphthalein or methyl orange)
• Add the acid into the burette and note the starting volume
• Add the acid very slowly from the burette to the conical flask until the
indicator changes to appropriate colour
• Note and record the final volume of acid in burette and calculate the
volume of acid added (starting volume of acid – final volume of acid)
• Add this same volume of acid into the same volume of alkali without the
indicator
• Heat to partially evaporate, leaving a saturated solution
• Leave to crystallise decant excess solution and allow crystals to dry
