Home > Community > Given this liquid-liquid phase diagram, is the green line the nitrobenzene-rich phase?
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Loveleen Bajaj

Given this liquid-liquid phase diagram, is the green line the nitrobenzene-rich phase?

Curtis Childress  Follow

first of all, the picture should have two arrows on top of the bars that are perpendicular (ie parallel to each other), because those represent the two components. Lets just call one A and the other B. If you choose a point on the right hand side of the curve, it means that you have little of component B that is "rich in" component A.

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Brian Arbenz  Follow

Here is the same diagram with more annotation from the physical chemistry textbook by Atkins:

phase diagram

It shows that above the temperature $T_{uc}$, there is only one phase (the substances mix in any ratio). Below that temperature, there are two phases, with compositions shown by the solid lines. The horizontal line shows that if you try to make a mixture with a mole fraction of $a$ at the given temperature, you will get two solutions with mole fraction $a'$ and $a''$ instead. You can calculate the approximate ratio of the volumes using this technique.

Am I right in assuming that the right side (green line) is the nitrobenzene rich phase?

Yes, because the x-axis is the mole fraction of nitrobenzene, the phase with higher fraction of nitrobenzene will be that on the right, as you say. It does not necessarily mean that the fraction is higher higher than 50% on the right and lower than 50% on the left, though.

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