Liquid-liquid solutions are considered ideal if their vapor pressures obey Raoult’s law. A liquid-liquid solution composed of 0.54 water and 0.46 propanol (C3H7OH), in mole fractions, has a vapor pressure of 81.6 torr at 45oC. The vapor of pure water and pure propanol at 45oC is 71.9 torr and 74.0 torr, respectively. Determine whether the above water-propanol solution is ideal, non-ideal with a positive deviation, or non-ideal with a negative deviation. Explain. (A) Ideal solution; the observed vapor pressure of 81.6 torr is equal to the calculated vapor pressure. (B) Non-ideal with positive deviation; the observed vapor pressure is higher than calculated. (C) Non-ideal with negative deviation; the calculated vapor pressure is higher than observed. (D) Non-ideal with positive deviation; the calculated vapor pressure is lower than observed.

According to Dalton law of partial pressure the total pressure of solution in container is equal to partial pressure of each component present in the solution. Ptotal = P1 + P2 Where P1 , P2 are the partial pressure of component 1 and 2. As we know Partial vapour pressure is directly proportional to mole fraction P1 = χ1 P°1 - (1) P2 = χ2 P°2 - (2) Where P°1 and P°2 are vapour pressure of pure component 1 and 2 which is 71.9 and 74.0 torr (given) χ2 and χ1 are the mole fraction of component 1 and 2 which is 0.54 and 0.46 . (given) Putting equation (1) and (2) in above formula P total = χ1 P°1 + χ2 P°2 PT = 0.54 × 71.9 + 0.46 × 74 PT = 72.866 torr Pobserved = 81.6 torr Pcalculated = 72.866 torr Therefore Pcalculated < Pobserved Therefore the calculated vapour pressure is lower than the observed vapour pressure , therefore show non - ideal positive deviation Therefore option ( d) is the correct one .

Answered: Liquid-liquid solutions are considered…

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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Liquid-liquid solutions are considered ideal if their vapor pressures obey Raoult’s law. A liquid-liquid solution composed of 0.54 water and 0.46 propanol (C₃H₇OH), in mole fractions, has a vapor pressure of 81.6 torr at 45^oC. The vapor of pure water and pure propanol at 45^oC is 71.9 torr and 74.0 torr, respectively. Determine whether the above water-propanol solution is ideal, non-ideal with a positive deviation, or non-ideal with a negative deviation. Explain.

(A) Ideal solution; the observed vapor pressure of 81.6 torr is equal to the calculated vapor pressure.

(B) Non-ideal with positive deviation; the observed vapor pressure is higher than calculated.

(D) Non-ideal with positive deviation; the calculated vapor pressure is lower than observed.

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