Gases that are more dense than air are collected by Adownward delivery Bupward delivery

Analysis of the Problem

To determine how gases that are more dense than air are collected, we consider the properties of gases and their behavior relative to air.

Relevant Concepts

1. Density of Gases: Gases that are more dense than air will tend to sink, as they are heavier than the surrounding air.
2. Gas Collection Methods: There are primarily two methods for gas collection based on their density relative to air:
   • Downward delivery (for dense gases)
   • Upward delivery (for less dense gases)

Conclusion

Since gases that are more dense than air will sink, the most appropriate method for collecting them is A. downward delivery. This method utilizes the tendency of denser gases to move downward, effectively gathering them in a container positioned below. In contrast, upward delivery is used for lighter gases, which rise above air.

Final Answer

A. downward delivery