2 H2(g) + O2 (g) --> 2 H20 (1) How many moles of hydrogen gas do you need to make 2 moles of liquid water?

Give more examples of this type of heat transfer:

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).

How many moles are in 1.26*10^24 particles in significant figures