Consider a process in which ethanol is added to water at T = 298 K and P = 0.1 M

Question

Consider a process in which ethanol is added to water at T = 298 K and P = 0.1 MPa. Pure water (MW = 18.015 g / mol) has density of 0.997 g / cm^3 and pure ethanol (MW = 46.07 g / mol) has a density of 0.789 g / cm^3.

A) What is the partial molar volume of pure water (in cm^3 / mol = ml / mol units).

B) When 0.1 mole of ethanol is added to 10 moles of water, the total volume of the system is found to increase by 5.51 cm^3. Use this experimental result to estimate the partial molar volume ethanol in water (in cm^3 / mol units).

C) Note that the partial molar volume of a solute is expected to depend on the solvent in which it is dissolved. How does the partial molar volume of ethanol in water [which you obtained in (b) above] compare with the partial molar volume of pure (obtained from the density of pure ethanol)?

Explanation / Answer

a) Molar Volume of water = MW/density = 18.07 cc/mole

b) Volume of solution = nA*VA + nB*VB

Partial Molar Volume of ethanol =VB = 5.51/0.1 = 55.1 cc/mol

C) Partial Molar Volume of pure ethanol = 46.07/0.789 = 58.39

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