How do I determine how many pounds of propane will be left in an "empty" tank at a given temperature?

Question

My grill runs on propane and I understand that when the tank is "empty" there is still some propane in it, there is just not enough pressure to allow it to escape. In a standard 20 lb tank what is this amount of propane left in an empty tank when the tank is at room temperature. When the tank is in a cold outdoor environment, there will be more propane left in the tank when it is "empty" than in a warm environment. How do i determine the amount of propane left in the tank at different temperatures?

Answer 1

A liquid will weigh the same at any temperature. You do not loose mass, your pressure changes.

If you want to know how much gas remains, weigh the tank. Pressures and temperatures will not provide you with relative mass.

Answer 2

You need a hobby. If it feels empty it's empty. Volume is the same in hot or cold. Pressure will be higher the higher the temp. Example: A propane grill will not work outside at the artic circle without heating the tank.