posted by Dave .
I have another question.
So 1 kcal of heat is added to 1.5 L of oxygen in a container at constant pressure. (1atm). Then volume increases to 3.1L. they want to know total energy change.
Now i think the formula is DH=DU + PDV
so what i did was DH = 1 kcal + 1atm(3.1-1.5) = 2.6 kcal...
its wrong... i don't know why please help!
Be careful with units and signs:
1) 1 L•atm = 24.2 calories
2) P•∆V work is done by the gas against the surroundings so it is negative: