Question

Review Constants Pe Consider the following two substances and their vapor pressures at 298 K All liquids evaporate to a certain extent. The pressure exerted by the gas phase in equilibrium with the liquid is called vapor pressure. Prap. The vapor pressure of a particular substance is determined by the strength of the intermolecular forces. But for any given substance, the vapor pressure only changes with temperature. The Clausius-Clapeyron equation expresses the relationship between vapor pressure and temperature: Substance Vapor pressure (mmHg) 275 450 In P, = In P +(#)(1-) B where and are the vapor pressures that correspond to temperatures Ty and T. respectively. AH,p is the molar heat of vaporization and R=8.3145 J/(mol-K) is the gas constant Based on this information, compare the characteristics of the two substances. Drag each item to the appropriate bin. View Available Hint's) Reset Help Has a higher heat of vaporization is a gas at 300 mming Has a higher boiling point Has weaker intermolecular forces Substance A Substance B Submit Part B The vapor pressure of dichloromethane, CH, Cl, at 0 °C is 134 mmHg. The normal boiling point of dichloromethane is 40 °C. Calculate its molar heat of vaporization Express your answer to three significant figures and include the appropriate units. View Available Hints) AH,up - Value Units Submit

Answer 1

Vapor pressure Pressure exerted by vapor of substance in equilibrium with by its condensed fhase I solid or liquid ) at a gewen temperature Boiling point Temperature at which vapor pressure of substance becomes equal to almost herie pressure Enthalpy of Vaporization Energy added to ligned to transform given amount of substance to vapor these Higher vapor pressure means intermoleculer love between ligued liquid molecules are weaker & hence suell energy is required for saporization ie to shvap is lower ! PÅ = 215 muntly Pop s 459 monthly Substance A Vapor pressure is less hence - . Has a higher Boiling point • Has higher heat of Vaporization Is a gas at 300 mmflg. Substance B Vapor pressure is high hence Has weaker intermolendar forces Applying Clausins Clapeyron equation bevepositation

P = Vapor pressure at timp To P = Vapor pressure at timp T2 R= 8.314 Imol-'kt P = 134 mmily P2 = 760 mm Hy Ta: 400 = 40+273 Ti 0°C = 273k. - 313K for boiling points Vapor pressure = atmospheric pressure= 766 monthly In 134 - Shuap (1 - 1 1 160 8.314 1313 273 ) - 1.735² aluap & -4.60 x 10-4 8.314 shvap: 1.735X 8.314 4.68x10-4 = 30,814.6 J/mol = 30.8kJ/