Vapor density is defined as the density of a gas in relation to which reference?

Vapor density is defined as the density of a gas in relation to which reference?

• A. Air
• B. Water
• C. Vacuum
• D. Another gas

Answer: (A)

Vapor density is the ratio of the density of a gas to the density of air at the same temperature and pressure. Using air as the reference lets us understand how a vapor will behave in the atmosphere: if the vapor’s density is greater than air, it will tend to settle in low areas; if it is less than air, it will rise and disperse. Using water, vacuum, or another gas as the reference wouldn’t describe how the vapor moves relative to the surrounding air in typical environmental conditions, which is why air is the standard reference.

Vapor density is the ratio of the density of a gas to the density of air at the same temperature and pressure. Using air as the reference lets us understand how a vapor will behave in the atmosphere: if the vapor’s density is greater than air, it will tend to settle in low areas; if it is less than air, it will rise and disperse. Using water, vacuum, or another gas as the reference wouldn’t describe how the vapor moves relative to the surrounding air in typical environmental conditions, which is why air is the standard reference.