How does chlorine gas compare to air in terms of weight?

Chlorine gas is indeed heavier than air, which is why this answer is correct. The molecular weight of chlorine is approximately 35.5 g/mol, while the average molecular weight of air—primarily a mixture of nitrogen and oxygen—is about 29 g/mol. This difference in molecular weights leads to the conclusion that chlorine gas will settle lower in the atmosphere compared to air, which can be critical in managing safety and ventilation in environments where chlorine gas is used or stored.

Understanding the weight differences between gases is important in wastewater treatment and associated processes, as heavier gases can accumulate in lower areas, posing safety risks. In contrast, lighter gases would rise and disperse more readily into the atmosphere.