Calculate the atomic mass of oxygen if the three common isotopes of oxygen have masses of 15.995 amu (99.759% abundance), 16.995 amu (0.037 % abundance), and 17.999 amu (0.204 % abundance).

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).