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Multiple Choice
The vapor pressure of dichloromethane, CH2Cl2, at 0°C is 134 mmHg. The normal boiling point of dichloromethane is 40°C. Calculate its molar heat of vaporization using the Clausius-Clapeyron equation.
A
45.3 kJ/mol
B
28.7 kJ/mol
C
15.2 kJ/mol
D
60.1 kJ/mol
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1
Understand the Clausius-Clapeyron equation, which relates the vapor pressure and temperature to the molar heat of vaporization. The equation is: , where is the vapor pressure, is the temperature in Kelvin, is the molar heat of vaporization, and is the universal gas constant.
Convert the temperatures from Celsius to Kelvin. The temperature at 0°C is 273 K, and the normal boiling point at 40°C is 313 K.
Use the given vapor pressure at 0°C, which is 134 mmHg, and the vapor pressure at the boiling point, which is the atmospheric pressure of 760 mmHg.
Rearrange the Clausius-Clapeyron equation to solve for the molar heat of vaporization, . The equation becomes: .
Substitute the values into the rearranged equation: is 8.314 J/mol·K, is 313 K, is 273 K, is 134 mmHg, and is 760 mmHg. Calculate .