Chem 125 Quiz #1 BenDr. 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 Watery = -5220x + 20.7R2= 0.99990.01.02.03.04.05.06.07.00.00250.00300.00350.00401/Temperatue (K-1)ln Pvap(P in torr)a. What is the heat of vaporization (in kJ/mole) for water? Graph is Clausis-Clapeyron graph: ln P = (-∆Hvap/R)(1/T) + C so slope = (-∆Hvap/R) -5220 = -(∆Hvap/R) = -(∆Hvap/8.314 J/mole·K) ∆Hvap= 433399 J/mole x (1 kJ/1000 J) = 43.4 kJ/moleb. 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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