I got 4.08 for the buffer and did it by:
[H+] = (Ka x [CH3CH2COOH[)/[CH3CH2COO-]
[CH3CH2COOH-] is just the concentration of NaOH.
You don't even need to find the concentrations as the volumes cancel out in the equation, I checked it and got the same answer with the number of moles and concentrations.
And was it dehydration or elimination in the type of mechanism question?
Think I did quite well, completely failed on the total pressure question, got like 600 or something O_O