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March 28, 2017

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(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

  • chemistry - ,

    HYDROGEN STORAGE IN ALLOYS - THE FUTURE? (10/10 points)
    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 half the surface concentration after 1 hour? (Express your answer in centimeters). Assume the diffusivity of hydrogen in the alloy is 3.091x10-6 cm2/sec. Use the approximation erf(x) = x for x with values between 0 and 0.6, if appropriate. Use the Erf Table on the Course Info page for values greater than 0.6.

    0.105 - correct

    The activation energy for H diffusion in LaNi5 is 0.25 eV. How far will the H diffuse (where will it reach half the surface concentration) if the experiment above is repeated at 35┬░C? (Express your answer in centimeters).

    0.124 - correct

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