Any fuel-oxygen mixture that contains more oxygen than is needed to burn the fuel completely is called a lean mixture, and a mixture containing too little oxygen to allow complete combustion of the fuel is called a rich mixture. A high-performance heater that burns propane, C3H8(g), is adjusted so that 100.0 g of O2(g) enters the system for every 100.0 g of propane. Is this mixture rich or lean