Thursday, 19 February 2015

8.1.2 - Laboratory Activity : Preparation of non-potassium and non-sodium soluble salts.

Laboratory Activity 8.1.2:
Preparation of non-potassium and non-sodium soluble salts.
Aim: To prepare zinc sulphate through the reaction between an acid and a metal oxide
» Sulphuric acid (1M)
» Zinc oxide

» Conical flask
» White tile
» Beaker
» Glass rod
» Bunsen burner
» Filter funnel
» Filter paper
» Measuring cylinder (100cm3)

1. 25cm3 of 1M sulphuric acid is put in a beaker and is heated.
2. Using a spatula, zinc oxide powder is added a little at a time, into the hot sulphuric acid while stirring continuously with a glass rod. The addition of zinc oxide is stopped when some white solids remain undissolved.
3. The mixture is filtered to remove the excess zinc oxide.
4. The filtrate is evaporated until a saturated solution (⅓ of original volume) of zinc sulphate is obtained.
5. The saturated solution is allowed to cool down until white crystal are formed.
6. The salt crystals are filtered, washed with a little distilled water and dried with filter paper.

Zinc oxide is a white powder. It dissolves in sulphuric acid to for a zinc sulphate solution The equation for the reaction is as follows:
ZnO(s) + H2SO4(aq) → CuSO4(aq) + H2O(l)

Excess zinc oxide is used to ensure that all the sulphuric acid is reacted, so as not to be present as an impurity in the zinc sulphate solution formed. The insoluble excess zinc oxide is then removed from the zinc sulphate solution by filtration.

Zinc sulphate can also be prepared by the reaction between sulphuric acid and zinc carbonate or metal zinc.

Zinc sulphate can be prepared by the reaction between zinc oxide and sulphuric acid.

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