7. Given the following sxperimental data for temperature and Pap for an unknown

Question

7. Given the following sxperimental data for temperature and Pap for an unknown liquid: Trial Pap (mmHg) TOC) 2.05 115.02 645.25 779.65 1010.01 225.25 247.95 300.0 318.14 345.85 -360.15 )Determine the molar heat of vaporization for an unknown liquid graphically as described in the data analysis section of this experiment. You will need to prepare a graph like in the experiment for this question, and use information found only on the graph to calculate to experimental error, but is an answer for this question. This may not appear linear due linear f or the calculation of AHvap DO NOT use the "two point" method. Print and attach the graph to your prelab. Remember that this is an individual assignment and must be your own work! Show your calculations with all units here as always. Make sure that the data table you made in Excel is printed on the same page as the graph, and your name is in the Excel file! AHva,- ole for this unknown liquid. b) Which trial in the table on this page above is closest to the normal boiling point of this liquid? HINT: No calculation is required to find the point closest to the normal boiling point. Trial is closest to the normal boiling point of this unknown liquid. EXPLAIN Fall 2017 Prelab Experiment 11

Explanation / Answer

since d(lnP)= (deltaH/RT2)dT

when integrated, lnP= -deltaH/RT+C where C is constant and P is vapor pressure, deltaH is latent heat of vaporization

so a plot of lnP vs 1/T ( T in kelvin) gives straight line whose slope id deltaH/R.

-deltaH/R= slope of the curve= -12358

deltaH= 12358*8.314 J/mole=102744 J/mole= 102.744 Kj/mole

Normal boiling point is defined as the temperature at which the vapor pressure becomes equal to 1 atm, i. e 760 mm Hg. the closest temperature is 345.85 deg.c

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