Answer:
9.1 × 10^-4m
Explanation:
From Fick's first law of diffusion:
J = -D dc/dx
Where J ,= diffusion flux
D = diffusion coefficient and dc/dx = concerntration gradient
Since we can assume a linear concentration profile, we rewrite the equation above as:
J = - D ◇c/◇x = -D (Cs - Cx)/(0 - x)
Where Cs = surface concerntration
C = concerntration of depth
X = target variable
J = diffusion flux = 1.0×10^-7kg/m^2/s
D ,= diffusion coefficient = 7.0×10^-12m^2/s
Substituting into the equation
1.0 ×10^-7 = (-7.0×10^-11)(4.9 -3.6) / ( 0 - X)
1.0 × 10^-7 = (-9.1 ×10^-11)/(0 - X)
Cross multiply
(1.0 ×10^-7) ×(0-X) = (-9.1 ×10^-11)
X = (-9.1 × 10^-11)/(-1.0 × 10^-7)
X = 9.1 × 10^-4m
