Expansion and Extension of Liquid Saturated Vapor Measurement Experiment
The expansion and extension of the liquid saturated vapor pressure measurement experiment involves determining the saturated vapor pressure of a liquid within a certain temperature range and using the Clausius-Clapeyron equation to obtain the molar evaporation enthalpy. Since the molar evaporation enthalpy is a function of temperature, its values differ in different temperature ranges, resulting in relatively large relative errors. The method of selecting temperature ranges based on the calculation of molar evaporation enthalpy to reduce experimental errors has not been applied in experimental teaching. In this experiment, pure water is chosen as the research object instead of organic reagents, and the average molar evaporation enthalpy of water in different temperature ranges is calculated using the method of Kirchhoff's law, which serves as a reference to determine the optimal temperature measurement range. Furthermore, the determination of the saturated vapor pressure of pure liquid is expanded to electrolyte and non-electrolyte solutions using Raoult's law, which can be linked to more theoretical teaching content. The experimental results show that the error in measuring the saturated vapor pressure of pure water within the range of 40–60 ℃ is small, and the molar evaporation enthalpy obtained using the experimental results is in good agreement with the calculated value, with an error of only 0.465%. Expanding this method to the determination of the saturated vapor pressure of sucrose and NaCl solutions can further verify the necessity of introducing activity coefficients in Raoult's law and the importance of studying non-ideal dilute solutions. In addition, using virtual simulation technology to demonstrate the flow of gas molecules and the change in system pressure in the static method can enhance visualization and make the experimental principle clear and easy to understand.