# Chemistry

posted by
**Andrea** on
.

The Gaussian error function can be approximated for small values of x as erf(x)≈x. Suppose a silicon wafer is exposed to aluminum vapor at 1300∘ C. At what distance (in centimeters) will the concentration of Al be 35% of the surface concentration in 164 hours? Assume the diffusivity of Al in Si is 10−10 cm2/s at 1300∘ C.

Give your answer in scientific notation, up to two decimal points in unit centimeters.