Experiment: Laboratory preparation of manganese II sulphate

Introduction

This is an example of forming a water soluble salt from an acid and a water insoluble base since all bases containing manganese are not soluble in water, e.g. manganese (II) oxide and manganese (II) carbonate. Any acid may be used and the final product will depend on the nature of the acid.

Safety considerations

All acids are corrosive and adequate safty precautions must be taken. Manganese salts are poisonous by ingestion and skin absorption

Therefore a filtration step is needed.

Instructions

1. Measure out 50cm3 dilute (bench) sulphuric acid into 250cm3 beaker

2. Warm the acid to about 70ºC using a bunsen burner, tripod and gauze.

3. Add manganese II carbonate one spatula at a time stirring throughout until no bubbles are observed on a further addition.

4. Filter the hot solution into an evaporating basin.

5. Allow to evaporate slowly in a warm place. (This last stage may be performed more rapidly using a water bath although the crystals produced will be smaller and there is a danger of decomposition)

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