Look at the given diagram and answer the following question: The apparatus is set up for the preparation of a certain gas in the laboratory. Which gas is this?

The apparatus is set up for the preparation of hydrogen gas in the laboratory. Hydrogen gas is prepared in the laboratory by the action of the dilute sulphuric acid on granulated zinc. Granulated zinc is ideal for the preparation of hydrogen gas in chemical laboratories because it usually contains a small amount of copper, which has the ability to act as a catalyst to the associated chemical reaction.

Look at the given diagram and answer the following question: Why is the evolved gas not being collected in the gas jar?

The evolved gas not being collected in the gas jar directly as it contains air. We collect the gas in the jar through downward displacement of water. Air is absorbed by the water and hydrogen gas being lighter than water comes out over water.