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Quiz1_Ben_key - Chem 125 Winter 2008 Quiz#1 Ben Dr Retsek...

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Chem 125 Quiz #1 Ben Dr. Retsek Winter 2008 NAME: ___ KEY _____________________________ 1. (10 points) Using the graph below for water answer the following two questions. Linear Relationship between Pressure and Temperatue for Water y = -5220x + 20.7 R 2 = 0.9999 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0.0025 0.0030 0.0035 0.0040 1/Temperatue (K -1 ) ln P vap (P in torr) a. What is the heat of vaporization (in kJ/mole) for water? Graph is Clausis-Clapeyron graph: ln P = (- H vap /R)(1/T) + C so slope = (- H vap /R) -5220 = -( H vap /R) = -( H vap /8.314 J/mole·K) H vap = 433399 J/mole x (1 kJ/1000 J) = 43.4 kJ/mole b. Calculate the vapor pressure of water at 50 ° C? Just use equation, but T needs to be in Kelvin. ln P (or y) = -5220 (1/323 K) + 20.7 ln P = 4.53 P = 93.6 torr (units were given on y-axis of graph)
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