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Questions and Answers
Which substance has the highest vapor pressure at 25°C?
Which substance has the highest vapor pressure at 25°C?
- Diethylether (correct)
- Water
- Ethylene glycol
- None of the above
What is the correct mathematical form of the relationship between vapor pressure and temperature according to the Clausius-Clapeyron equation?
What is the correct mathematical form of the relationship between vapor pressure and temperature according to the Clausius-Clapeyron equation?
- $ ext{ln} P_{vap} = - rac{ ext{Constant}}{T} + C$ (correct)
- $ ext{ln} P_{vap} = - rac{ ext{Constant}}{T^2} + C$
- $ rac{1}{P_{vap}} = rac{ ext{Constant}}{T} + C$
- $P_{vap} = - rac{ ext{Constant}}{T} + C$
At what temperature do all three substances generate vapor pressure based on provided data?
At what temperature do all three substances generate vapor pressure based on provided data?
- 0°C
- 25°C (correct)
- 100°C
- 197.3°C
Why is it important to convert temperature to Kelvin when using the Clausius-Clapeyron equation?
Why is it important to convert temperature to Kelvin when using the Clausius-Clapeyron equation?
What does the enthalpy of vaporization ($ ext{ΔH}_{vap}$) relate to in the context provided?
What does the enthalpy of vaporization ($ ext{ΔH}_{vap}$) relate to in the context provided?
Flashcards
Vapor Pressure
Vapor Pressure
The pressure exerted by the vapor of a liquid in equilibrium with its liquid phase at a given temperature.
Normal Boiling Point
Normal Boiling Point
The temperature at which the vapor pressure of a liquid equals the atmospheric pressure.
Clausius-Clapeyron Equation
Clausius-Clapeyron Equation
A mathematical equation that describes the relationship between vapor pressure and temperature. It relates the enthalpy of vaporization to the slope of the vapor pressure curve.
Enthalpy of Vaporization
Enthalpy of Vaporization
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How does temperature affect Vapor Pressure?
How does temperature affect Vapor Pressure?
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Study Notes
Vapor Pressure and Temperature
- Different substances have different vapor pressures at the same temperature
- The substance with the weakest intermolecular forces has the highest vapor pressure at a given temperature
- The graph of vapor pressure versus temperature is exponential
- The Clausius-Clapeyron equation allows for linearization of the vapor pressure curve:
- ln Pvap = -ΔHvap/RT + C
- where R is the ideal gas constant and C is a constant
- ΔHvap is the enthalpy of vaporization, T is temperature in Kelvin
- Using this equation, the vapor pressure can be predicted at temperatures below the normal boiling point.
- Measuring vapor pressure as a function of temperature helps determine the enthalpy of vaporization (ΔHvap), which reflects the energy required to overcome intermolecular forces in a liquid to convert it to a gas. This relates to molecular phenomena to bulk properties
Normal Boiling Point
- The normal boiling point is the temperature at which the vapor pressure of a liquid equals 1 atm.
- Different substances have different normal boiling points, influenced by the strength of intermolecular forces
- The substance with the weakest intermolecular forces will have the lowest normal boiling point at a given pressure.
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