Which of the following gases could be collected by downward displacement of air? Chlorine (Cl2), Hydrogen (H2), or Hydrogen chloride (HCl)?

Here are the solutions to the questions:

1. Which of the following gases could be collected by downward displacement of air?
Downward displacement of air is used to collect gases that are denser than air. The average molar mass of air is approximately $29 \text{ g/mol}$.

• A. Chlorine (Cl$_2$): Molar mass = $2 \times 35.5 = 71 \text{ g/mol}$. Denser than air.
• B. Hydrogen (H$_2$): Molar mass = $2 \times 1 = 2 \text{ g/mol}$. Less dense than air.
• C. Hydrogen chloride (HCl): Molar mass = $1 + 35.5 =