We're going to quickly summarize the module, and then do one final (slightly
extended) example using these equations, and comparing the performance of
the continuous and the discrete models.

...................... Review......

**The diffusion through a membrane equations:** diffusion is
driven by the difference in concentrations on the two sides of the membrane.
It is also affected by the permeability coefficient and the area of the membrane:

Continuous version |
||
---|---|---|

Discrete version |

The **permeability coefficient** is determined by the equation
P = KD/Δx.

The **concentrations that we need in order to calculate flux are in
moles/liter**. A mole is 6.022 * 10^{23} molecules (sixty trillion
trillion).

In order to convert between grams and liters, you need to know the **molecular
weight** of the substance, which is to say, how much a single mole
of that substance weighs. Molecular weight is calculated by multiplying the
number of times each type of atom appears in the equation by its molecular
weight, and adding it all up.

Multiplying grams by molecular weight will give you the number of moles of the substance. Then dividing by the volume of water will give you concentration in moles/L.

Moles per liter is sometimes called simply M.

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