20-VPressure-Prob

# 20-VPressure-Prob - VAPOR PRESSURE AND HEAT OF VAPORIZATION...

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VAPOR PRESSURE AND HEAT OF VAPORIZATION GCHEM II LAB CONCEPT PROBLEMS Raoult’s Law: VP TOTAL = Pp (A) + Pp (B) Pp (A) = [mole fraction (A) ] * [Vp (Pure A) ] Heat of Vaporization ( Hvap) = Heat required to vaporize one mole of liquid at a temperature Graphical Method to Calculate Heat of Vaporization ( Hvap): Plot lnP versus 1/T [y = m x + b] [lnP = ( Hvap) x 1/T + b] m = slope = ( Hvap) Hvap = –( slope) x R R R Clausius-Clapeyon Equation to Calculate Heat of Vaporization ( Hvap): ln (P 2 /P 1 ) = ( Hvap /R) (1/T 1 – 1/T 2 ) where: R=8.314 x10 -3 (kJ/moles-K), P 2 and T 2 > P 1 and T 1 1. A liquid solution of 78.4 grams of benzene (C 6 H 6 ) and 92.4 grams of toluene (C 7 H 8 ) is placed in a container open to the atmosphere at 20.0 o C. If the vapor pressure of pure benzene is (75.5 torr) and pure toluene is (22.6 torr), what is the partial pressure of the benzene over the solution and what is total pressure ? RAOULT’S LAW

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20-VPressure-Prob - VAPOR PRESSURE AND HEAT OF VAPORIZATION...

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