Why do cars need a cooling system in conjunction with the engine? a) the transformation of energy in the engine produces a lot of waste heat b) sunlight makes the engine heat up quickly c) friction from the road makes the engine hotter than is safe

Butane gas reacts with oxygen gas to give carbon dioxide gas and water vapor (gas). if you mix butane and oxygen in the correct stoichiometric ratio, and if the total pressure of the mixture is 390 mmhg, what is the pressure (in mmhg) of water vapor after the reaction is completed (temperature and volume do not change).