I am trying to calculate the pressure of a mainly two component mixture (propane/butane). I have an estimated composition and I want to calculate the pressure based on this estimated composition and see how it matches up to physically measured pressure. My problem is that I don't understand how I am supposed to find molar volume without knowing density which is a function of pressure. Second, will the form I posted of the PR EOS work if I input a molar volume of my mixture in the liquid phase? I have not gotten reliable results with that so far. Lastly, how do I finding overall V? currently I am calculating it like this xiMi/pavg.