Answer :
Final answer:
The Clausius-Clapeyron equation can be used to estimate the vapor pressure of ethanol at a given temperature using the substance's normal boiling point and molar enthalpy of vaporization, alongside known vapor pressures at different temperatures.
Explanation:
To estimate the vapor pressure of a substance at a given temperature when the normal boiling point and the molar enthalpy of vaporization are known, we can use the Clausius-Clapeyron equation. This equation relates the temperature, vapor pressure, and heat of vaporization of a liquid. While we don't have enough information to directly calculate the vapor pressure of ethanol at 30.0°C in the original question, we can use the provided data to estimate the enthalpy of vaporization for ethanol using the temperatures and vapor pressures given at 20.0°C and 63.5°C. This calculation would typically involve taking the natural logarithm of the ratio of the two vapor pressures and dividing by the difference in the reciprocals of the two temperatures (in Kelvin), then multiplying by the universal gas constant (R).