Which term specifically describes the ratio of the average molecular weight of a gas or vapor to the average molecular weight of air?

Which term specifically describes the ratio of the average molecular weight of a gas or vapor to the average molecular weight of air?

• A. Specific Gravity
• B. Specific Gravity of Water
• C. Specific Gravity of Air
• D. Relative Density

Answer: (C)

The concept being tested is how we name the ratio that compares a gas’s average molecular weight to the air around it. For gases at the same temperature and pressure, density is proportional to molecular weight, so the ratio of a gas’s average molecular weight to that of air tells us how heavy or light the gas is relative to air. This specific ratio is called the Specific Gravity of Air. It indicates buoyancy behavior: values greater than 1 mean the gas is heavier than air and tends to stay low, while values less than 1 mean it’s lighter and tends to rise. Some terms describe related ideas, but when the reference substance is air, the precise term used is Specific Gravity of Air.

The concept being tested is how we name the ratio that compares a gas’s average molecular weight to the air around it. For gases at the same temperature and pressure, density is proportional to molecular weight, so the ratio of a gas’s average molecular weight to that of air tells us how heavy or light the gas is relative to air. This specific ratio is called the Specific Gravity of Air. It indicates buoyancy behavior: values greater than 1 mean the gas is heavier than air and tends to stay low, while values less than 1 mean it’s lighter and tends to rise. Some terms describe related ideas, but when the reference substance is air, the precise term used is Specific Gravity of Air.