How much does a gallon of gasoline vapor weigh?

Answer 1

Briefly, the saturated vapor volume of an average gallon of liquid gasoline when fully evaporated is 160.4 gallons of vapor at 60° F and sea level.

Vapor volume of a liquid is the number of cubic feet of vapor resulting from the complete evaporation of the liquid. The vapor volume depends on parameters of density, temperature, pressure and molecular weight which is affected by the variety of formulas for gasoline that is comprised of a wide range of hydrocarbons.

Several approaches are available to solve this problem. One is shown below.


Using a common industrial formula:

one liquid gallon = [(8.31) x (SG) x (387 cu ft)] / (MW)

Where:

8.31 = pounds in gallon of water

SG = specific gravity of liquid being vaporized

387 = At standard conditions, one pound-molecular weight of a material will evaporate to fill 387 cubic feet of space.

MW= molecular weight of liquid being vaporized

Then using the approximate gasoline constants:

one liquid gallon of gasoline = [(8.31 pounds in a gallon of water) x (.70 approx. specific gravity of gasoline) x (387 cu ft)] / (105 molecular weight of average gasoline)

= 21.4 cubic feet of vapor volume

There is 7.481 U.S. gallons in one cubic foot.

So:

one liquid gallon of gasoline = (21.4 cubic feet) x (7.481)

= 160.4 gallons of saturated gasoline vapor

The vapor volume will vary based on the specific formulation of gasoline, pressure, and temperature.

D. Hollatz

Answer 2

Your question is not entirely clear, because I am not sure if you want to know what the weight is that results from vaporizing a gallon of gasoline, or if you want to know the weight of enough gasoline vapor to occupy a gallon of volume. I can answer both. The weight of a gallon of gasoline remains the same whether in liquid or gas form because it relates to linear logrithmic constant volume. As for the weight of the amount of gasoline vapor that fills a gallon of volume, that is highly temperature dependent. Current atmosphere temp and vapor temp and also vapor expands when heated. Size of molecules and number of molecules determines how much fits. Size of molecules is determined by system used to vaporize fuel.