Three identical closed containers are labeled A, B, and C, respectively. Each co
ID: 1052398 • Letter: T
Question
Three identical closed containers are labeled A, B, and C, respectively. Each container holds a pure liquid in equilibrium with it vapor. One container holds acetone, the second holds ethanol, and the third contains water. Each container is equipped with a pressure-measuring device that records the equilibrium vapor pressure. It is known that all containers are at the same temperature, but that common temperature is unknown. The partial molar enthalpies of vaporization are 44, 010 J/(mol K) for water, 30, 250 J/(mol K) for acetone, and 39, 322 J/(mol K) for ethanol. The normal boiling points are 373.15 K for water, 329.65 K for acetone, and 351.65 K for ethanol. Using these data and the measured vapor pressures alone, is it possible to determine which container holds which liquid? Discuss your analysis in detail and show that your conclusions are correct. You may assume that the partial molar enthalpies of vaporization are independent of temperature.Explanation / Answer
Yes. It is possible to identify the liquids based on th egiven information and the measured vapor pressures.
The liquids with lower boiling point have more vapor pressure at the same temperature than the liquids with higher boiling points.
Similarly higher enthalpy of vaporiation also indicates it is difficult to form the vapor than the ones with lower enthlapy.
Since water has the highest boiling point and highest molar enthalpy of vaporization, it shows the least measured vapor pressure.
Acetone is the liquid with lowest boiling point and lowest enthalpy of vaporization, it shows the highest measured vapor pressure.
Ethanol has moderate boiling point and enthalpy , its meaasured vapor pressure would be less than acetone but more than water.
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