Tetrachlorosilane (SiCl₄) gas is reacted with hydrogen gas (H₂) to produce electronic-grade polycrystalline silicon at 800°C and 1.5 × 10⁵ Pa according to the reaction equation:

SiCl₄(g) + 2H₂(g) → Si(s) + 4HCl(g).

The reaction rate may experience diffusion limitations at the growing Si solid surface. To address this concern, the diffusion coefficient coefficients in this system must be estimated.

a. Estimate the binary diffusion coefficient of SiCl₄ in H₂ gas.

b. Estimate the diffusion coefficient of SiCl₄ in a mixture containing 40 mole% SiCl₄, 40 mole% H₂, and 20 mole% HCl. Is this diffusion coefficient substantively different than the diffusion coefficient estimated in part (a)? The Lennard–Jones parameters for SiCl₄ are σ = 5.08 Å and ε/k = 358 K.