Final answer:
To calculate the mass of propylene glycol needed to reduce the vapor pressure of water, you would use Raoult's Law and follow steps involving mole fraction and molar calculations. However, the question lacks essential data for precise calculations.
Step-by-step explanation:
The subject of this question is the calculation of the mass of a solute needed to achieve a certain reduction in vapor pressure of the solvent, which is based on Raoult's Law in chemistry. To find the mass of propylene glycol needed to reduce the vapor pressure of water by 3.88 torr at 338 K, you would follow these steps:
- Compute the mole fraction of propylene glycol that corresponds to the decrease in vapor pressure.
- Calculate the moles of water present in 0.450 kg.
- Calculate the required moles of propylene glycol and convert this to mass using its molar mass.
However, there is not enough information provided in the question to perform the actual calculations, such as the vapor pressure of pure water at 338 K and any assumptions regarding ideal solution behavior.