Question

How much pv work is done in kilojoules for the reaction of 0.68 mol of h2 with 0.34 mol of o2 at atmospheric pressure if the volume change is -4.1 l ?

Answer 1

The delta H of -484 kJ is the heat given off when 2 moles of H2 react with 1 mole of O2 to make 2 moles of H2O. You don't have anywhere near that much reactants, only 1/4 as much

actual delta H = 0.34  moles H2 x (-484 kJ / 2 moles H2) = 823 kJ 

delta E = delta H - PdeltaV = 823 kJ - 0.41 kJ = 822 kJ