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Experiment 1

Making a soluble salt from a base

In this experiment you will be making a salt using a metal carbonate. The use of a metal carbonate allows us to easily see when all the acid has been used up in the reaction.

As the reaction proceeds the metal carbonate will neutralise the acid and form a soluble salt. However, when all the acid has reacted any excess metal carbonate will be left over.

We can use this to find out when all the acid has reacted and simply filter off the excess metal carbonate, leaving only the soluble salt and water behind.

Apparatus and chemicals

• 100 cm³ beakers (x2), glass rod
• Tripod, gauze, Bunsen burner, heat proof mat
• Filter funnel, filter paper and conical flask
• Evaporating basin
• Copper(II) carbonate (approx 4 g)
• Sulfuric acid (1 mol/dm³ 25 cm³)

Follow safety advice as given by teacher

Method

1. Place 4 g of copper(II) carbonate in a beaker.
2. Warm 25 cm³ of 1 mol/dm³ sulfuric acid in another beaker, the acid should be no hotter than 60^оC.
3. Add the copper(II) carbonate to the sulfuric acid and stir until there is no further reaction and unreacted copper(II) carbonate is present.
4. Allow to cool and filter the mixture and retain the filtrate.
5. Heat the filtrate in an evaporating basin on a tripod and gauze until the volume is about one half of what it was originally.
6. Allow the basin to cool and the crystals will form.
7. When the crystals have formed, filter if necessary, dry (between two sheets of filter paper or using a desiccator or in a low temperature oven).