4.7 describe experiments to prepare soluble salts from acids

Preparing soluble salts from acids

Acid + insoluble base

• Put some dilute acid into a beaker and heat it using a Bunsen burner flame. Do not let it boil.
• Add the insoluble base, a little at a time, to the warm dilute acid and stir until the base is in excess.
• Filter the mixture into an evaporating basin to remove the excess base.
• Leave the filtrate in a warm place so the water evaporates and crystals form.
• Remove the crystals and dry them on filter paper.

Acid + soluble base (alkali)

• Put an aqueous solution of the alkali into a conical flask and add a suitable indicator (e.g. litmus or methyl orange)
• Add dilute acid from a burette until the indicator just changes colour.
• Add powered charcoal and shake the mixture to remove the colour of the indicator.
• Filter to remove the charcoal and then obtain crystals from the filtrate in the usual manner.