In the gas specific gravity equation Yg = ?g / ?air, what does Yg represent?

• A. The density of the gas
• B. The density of dry air
• C. The specific gravity of the gas
• D. The molecular weight of the gas

Answer: (C)

The main idea is comparing how heavy a gas is to air. Yg is the gas specific gravity, defined as the ratio of the gas density to the density of dry air at the same temperature and pressure. Because it’s a ratio, Yg is dimensionless and shows whether the gas is heavier or lighter than air. It’s not the actual density itself, nor the density of air, and while the density ratio can relate to molecular weights under the same conditions, the quantity described by that equation is specifically the gas’s specific gravity.