posted by mel .
A 75.0 L stainless steel container was charged with 3.00 atm of hydrogen gas and 4.00 atm of oxygen gas. A spark ignited the mixture, producing water.
What is the pressure in the tank at 25°C?
What is the pressure in the tank at 125°C?
Write the equation and balance it.
Calculate n for H2 and n for O2 and change these to concentration in mols/L.
Determine the limiting reagent.
Determine how much of the other reagent remains after the reaction.
Convert molarities remaining and formed into mols (mol/L x 75 L = mols.
Convert mols H2O to grams. The number I have seems to be small enough to ignore it (that is, it won't take up much volume) but you need to verify that. I have also ignored the vapor pressure of water for the first part.
Then PV = nRT and use mols of the remaining reagent, V = 75 L, R and 298 K to calculate pressure. You probably need to confirm that the vapor pressure of the water can be ignored.
For the second part, notice that 125 C is enough to change ALL of the water to vapor so you have two contributors to the pressure. You should be able to do this on your own.
Check my thinking. It's late at night.