a) What are the metric and American engineering units of the diffusion constant?

b) What are the metric and American engineering units of a mass transfer coefficient?

c) Do you expect that in situations where the heat transfer coefficient is small, that the mass transfer coefficient would be small, too?

d) The highest thermal conductivities are found in coinage metals like gold, silver and copper, and gasses have some of the lowest thermal conductivities. Do you expect these to have the highest (metals) and lowest (gasses) diffusivities as well? What does this tell you about the molecular mechanisms of heat vs. mass transfer?

e)Think about Fig. 2.2-2 in your text. How can matter diffuse from a region of low concentration to one of higher concentration? Is there an analogous situation in which heat is conducted from a region of low temperature to one of higher temperature? Can you provide a thermodynamic argument for this based on how the chemical potential depends on concentration (say, mole fraction) vs temperature?

f) Can the diffusion constant ever be negative? Why or why not?