Iron has a density of 11.6 g/cm3. What is the mass (in g) of a cube of iron with the length of one side equal to 5.7 mm?

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).