[asd]

can somebody explain the variation of molar volume with composition of liquid ?

[haz658]

Hello. I will take a crack at answering your question. By molar volume, I assume you mean the volume of 1 mole of the solution which is being described, and not the partial molar volume, the volume, per mole, of one of the components in that solution. If I am mistaken, please correct me. Does it make sense to you that molecules of some component (I'll refer to it as component A) could behave/interact differently amongst themselves than they would when added to a container with molecules of another component (component B)? Well there are several possible results when mixing these components A and B: A could interact with B in a more positive manner than it does amongst other A molecules, A could interact with B exactly the same as it does in the presence of other A molecules, and A could interact with B in a more negative manner than it does with other A molecules. Depending on the quality of the A-B interaction, A will arrange itself in a certain manner when mixed with B, and this will vary based on the identity of A and B. As a result, the volume of A in solution will not be the same as the volume-per-mole of A in pure liquid A. Again, this value will depend on the identities of A and B. The same is true of B, that is, B will arrange itself in a certain manner and its volume-per-mole will be affected as a result. Therefore, the total volume and, consequently, the volume-per-mole of solution will be affected by the mole fraction of each component in the solution, based on the following equation:

$$ V_{total} = V^{partial,mol}_{A} n_A + V^{partial,mol}_{B} n_B /$$

where n is the number of moles of the respective component in the solution and V^partial,mol is the partial molar volume of the respective component for a mixture with the other component. Therefore, the molar volume of the solution as a whole, will change with the mole fraction of one of the components.
        I hope that this has been helpful. If I made a mistake or if my method of responding to the question was improper, please inform me.
                                                      -Matt