3) Data for the vapor pressure of an unknown liquid are given below T (C) p (tor

Question

3) Data for the vapor pressure of an unknown liquid are given below T (C) p (torr) T (°C) p (torr) 51.7 58.1 64.8 245 281 358 459 67.7 76.2 79.6 81.2 496 655 722 765 The above data can be analyzed by the Clausius-Clapeyron equation. According to that equation d (IT) R where p is the vapor pressure, T is the absolute temperature (in K), and AH° vap is the enthalpy of vaporization for the liquid. Therefore the slope in a plot of In(p) vs 1/T can be used to find the enthalpy of vaporization for the liquid a) Plot the above data by hand according to eq 3.1. You may use the data plot in the sample lab report asa guide. You will normally be allowed to use EXCEL or other plotting programs for data plots in your lab report, but for this problem I am requiring that you do the plot by hand. I will provide you with graph paper for your plot. b) Find the best fitting line to the above data (slope and intercept, including correct units) c) Based on your answer in b, find Hovap (including correct units).

Explanation / Answer

a plot of lnP vs 1/T is generated and shown below along with data points.

the plot of lnP vs 1/T gives straight line whose slope is -deltaH/R, R = gas constant = 8.314 J/mole.K and deltaH= latent heat of vaporization

Equatino of best fit is lnP= -3842*1/T+17.48

from the equation of best fit, the slope = -deltaH/R= -3842 and deltaH= 3842*8.314 J/mole =31942.4 J/mole= 31.942 Kj/mole ( 1000J= 1KJ)

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