The discussion centers on the relationship between partial pressure (P) and mole fraction (χ) in a mixture, specifically addressing the claim that the graph of P vs. χ cannot pass through the origin. Participants argue that at a mole fraction of zero, the partial pressure must also be zero, making the graph's behavior at this point logically inconsistent. The consensus is that a P vs. χ plot is only meaningful for values where the substance is present, reinforcing the idea that a mole fraction of zero renders the graph irrelevant for that component.
PREREQUISITESChemistry students, chemical engineers, and professionals involved in thermodynamics and phase equilibria will benefit from this discussion.
Borek said:Molar fraction of zero means there is no substance present, that's perfectly logical to me.
What you are saying is that you object to extending the relationship p = Px down to x = 0, even though at x = 0, the species is not present so that its partial pressure p is equal to zero ( p = 0). And somehow this objection makes sense to you (because it doesn't make sense to me). I'm totally in agreement with Borek.T Damen said:That is perfectly logical of course..
But imagine a P, xi plot for substance x in a mixture. At xi=0 the plot is not meaningful for describing substance x anymore cause substance x is not present anymore.
Simply put: a P, xi plot for a certain substance can only be plotted for values of xi where the substance is actually present.