# Passive transport

1. Feb 23, 2009

### superwolf

1. The problem statement, all variables and given/known data

2. The attempt at a solution

a) The particle seems to be 50 nm in diameter, so

$$D = \frac{k_BT}{6 \pi \eta R} = 4.4E-12 m^2s^{-1}$$

b)

$$j_{diff}=-D\frac{dc}{dx} = -4.4E-12 \cdot \frac{dc}{dx}$$

I don't know what to do next...Can I assume $$c(x) = c_0x$$? In that case,

$$j_{diff} = -4.4E-12 c_0$$

Is this correct? What are the units?

And how to do c)?

Last edited: Feb 23, 2009
2. Feb 23, 2009

### siddharth

What does the continuity equation tell you about the flux in the tube? Hint: Fick's Second Law