Question

Write Down The Reason Why.

1-1. the energy of formation is higher for a self-interstitial defect compared to a vacancy defect.

1-2. one polish must be a metal, then etch it, to observe the grain boundaries in the optical microscope.

2. In the classic J, E activates a chemical weapon so she can escape. In this case, a reactive chemical was inserted in the top of a 10 cm cylindrical vessel containing a polymer core, saturating the top surface. Critical mass is achieved when a point 0.5 cm from the surface reaches 5% reactant concentration, igniting the weapon. E laughs at you and says, “Good luck saving the city; you may want to try the landfill an hour away. But, I don’t think you’ll make it. The diffusion coefficient is 5.1 x 10-9 cm2 /s!”

2-1. Is E correct? Can you save the city? How?

2-2. If you needed to slow the diffusion down from above, how would you do it?

3. What is the difference between Fick’s First and Second Laws?

Answer 1

3)

Fick’s first law tells us that the flux goes from regions of high concentration to low concentration with a magnitude that is proportional to the concentration gradient. Here the diffusion coefficient is proportional to the square of velocity of diffusing particles, which depends on the temperature and pressure. And the diffusion coefficient is only true for dilute solutions.

Fick’s second law of diffusion is a linear equation with the dependent variable being the concentration of the chemical species. Here the diffusion of chemical species occurs independently. Here all diffusion coefficients are equal and independent of temperature and pressure.