Describe the laboratory preparation of hydrogen gas, including the apparatus and the reason for heating wet sand.

a) To complete the diagram for the laboratory preparation of the gas (hydrogen):

1. Add a retort stand and clamp to securely hold the test tube in a horizontal or slightly inclined position.
2. Place a Bunsen burner under the wet sand to heat it and generate steam.
3. Place a second Bunsen burner under the zinc granules to heat them to a high temperature.
4. Extend the delivery tube from the test tube into a trough of water.
5. Position an inverted gas jar over the end of the delivery tube in the trough of water to collect the hydrogen gas by downward displacement of water.

b) It was necessary to heat wet sand before heating Zinc granules to generate steam, which serves to expel all air from the reaction tube and delivery tube. This prevents the formation of an explosive mixture of hydrogen gas and air when hydrogen production begins.