$1.$

a$.$ For a given material, which gas will have a faster diffusion rate$-$helium or nitrogen? Explain your answer.

b$.$ Determine the diffusion coefficient for zinc diffusing into copper at $200\backslash$deg C$.$

c$.$ Create a plot showing diffusion coefficient vs$.$ temperature for zinc diffusing into copper over the range of $0\backslash$deg C to $600\backslash$deg C$.$ Include a minimum of six data points $($you may use Excel for the repetitive calculations$).$ What does the shape of the curve tell you about the dependence of diffusion rate on temperature?

d$.$ Determine the diffusion coefficient for nickel diffusing into copper at $200\backslash$deg C$.$ Explain why the value differs from that found in Part a$.$