Final answer:
To determine the diffusion flux of water vapor through a polypropylene sheet, Fick's first law of diffusion and the ideal gas law are utilized, taking into account the pressure difference, sheet's thickness, and temperature, along with necessary unit conversions.
Step-by-step explanation:
The student is asked to calculate the diffusion flux of water vapor through a polypropylene sheet at a steady state, given a pressure difference across the sheet, the sheet's thickness, and temperature.
To calculate the diffusion flux, we will use Fick's first law of diffusion, which relates the diffusion flux to the concentration gradient (or in this case, the pressure gradient) and the material's diffusion coefficient.
The formula for Fick's first law in one dimension is J = -D (dC/dx), where J is the diffusion flux, D is the diffusion coefficient, dC/dx is the concentration gradient, and the negative sign indicates that diffusion occurs from high concentration to low concentration.
Given the pressure gradient instead of the concentration gradient, we can express the concentration gradient in terms of pressure using the ideal gas law, as the concentration is proportional to the pressure at a constant temperature.
To calculate the diffusion flux in the required units of (cm3 stp)/cm2-s, we also need to apply unit conversions and possibly the use of known material properties or empirical data for the diffusion coefficient of water vapor in polypropylene at the given temperature.