Excellent example of Basement Internet Intellectual Wordsmithing. Believing if one chains pretty words together that one creates a new reality. The truth is we are all Muggles and can not create such things with words the way wizards can.
"Burning" is oxidation. The addition of oxygen. The 20 pounds of CO2 consists mostly of air which was originally in the chamber. Except as others have pointed out the combustion will not be complete because the gasoline ran out of oxygen.
"Conservation of Mass. Its the law." You can not create or destroy mass without an atomic event.
Want another exercise? Consider a room with perfect thermal isolation. A refrigerator is running inside the room with its door open. Tomorrow will the room be A) hotter, B) colder, or C) the same temperature?