Posted by **Andrea** on Thursday, December 6, 2012 at 6:38pm.

(a) Certain alloys such as LaNi5 can store hydrogen at room temperature. A plate of LaNi5 containing no hydrogen is placed in a chamber filled with pure hydrogen and maintained at a constant pressure. At what depth from the surface will the concentration of hydrogen be 1/2 the surface concentration after 1 hour? Assume the diffusivity of hydrogen in the alloy is 3.091×10−6 cm2/s. Use the approximation erf(x)≅x for 0<x<0.6 if appropriate.

Give your answer in unit centimeters with up to three decimal spaces

(b) The activation energy for H diffusion in LaNi5 is 0.25 eV. How far will the H diffuse (where will it reach 1/2 the surface concentration) if the experiment in part a is repeated at 35∘ C?

Give your answer in unit centimeters with up to three decimal spaces