Question

A diffusion coefficient KG was determined for the diffusion of a gas A through a stagnant film B [KG = 0.88 mol//h-ft2-atm].

What is the flux of A from a surface into a mixture of A & B, where B can dissolve into A as A diffuses from the surface?

Conditions at the surface PA1 = 0.2 atm @ P = 1 atm

Conditions in the bulk PA2 = 0.05 atm & PB2 = 0.95 atm

Answer 1

Step-by-step explanation:

Transfer of mass A into stagnant film B depends on the availability of driving force.

Whereas driving force is the pressure difference at the surface of A and the bulk.

As,
`N_(A) \propto (P_(A1) - P_(A2))`

`N_(A) = K_(G) * (P_(A1) - P_(A2))`

Therefore, putting the given values into the above formula as follows.

`N_(A) = K_(G) * (P_(A1) - P_(A2))`

=
`0.88 * (0.2 atm - 0.05 atm)`

= 0.132
`mol/h.ft^(2)`

Thus, we can conclude that the flux of A from a surface into a mixture of A and B is 0.132
`mol/h.ft^(2)`