Question

EXPERIMENT 7 Pre-Lab Assignment Determining the Empirical Formula of a Compound Name Date 1. Why is it important to scour the magnesium strip with steel wool at the start of the experiment? 2. Why must the heated crucible be cooled to near room temperature before weighing? 3. Should the Bunsen burner flame be kept heating one area of the crucible? Explain why or why not. 4. If the magnesium ribbon flares up, should you stare at it? Explain.

Answer 1

1. It is important to scour the magnesium strip with steel wool at the start of the experiment because when magnesium strips are in contact with the atmospheric oxygen, Mg reacts with oxygen to form MgO which appears as a coating on the ribbon. Hence intended results will not be obtained. Scouring the magnesium ribbon with steel wool removes this coating.

2. Because when the crucible is heated up the weighing machine gives a wrong reading. Heat from the crucible warms up the surrounding air, forming air currents which gives an fluctuating reading that is rising and falling.

3. No, the Bunsen burner flame should not be kept heating one area of the crucible. Because then it will cause the compound in a particular spot to get oxidised.

4. No, because burning magnesium ribbon causes the emission of UV light of sufficient intensity which can cause temporary loss of vision.