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Vijay A. Sethuraman, Ph. D.

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Sample Questions for the Admission to Candidacy Exam - October 27, 2004

These are some of the sample questions compiled a while ago by Professor Weidner. Though a student will routinely learn to answer these during the process of attending the three core ECHE courses: 700, 710 & 720, they don't necessarily define the scope of the AtC exam.

I. Chemical Process Analysis:

  1. Sketch the geometric interpretation of the mean value theorem of integral calculus. 

  2. Sketch the geometric interpretation of the mean value theorem of differential calculus. 

  3. What is an Eigen value? 

  4. What is an Eigen vector? 

  5. What is the characteristic equation of a matrix and how is it used? 

  6. What are the definitions of rank/transpose/adjoint/inverse/determinant of a matrix? 

  7. What is the Exponential Matrix? 

  8. What is the Matrizant? 

  9. How does one split a second order DE into two first order DE’s and proceed to solve the two first order DE’s by the matrix exponential method? 

  10. How is the Laplace transformation used in solving PDE’s? 

  11. What is the Gauss Newton Method for Non-Linear parameter estimation? 

  12. What are sensitivity equations and sensitivity coefficients? 

  13. Give the definitions of erf(x) and erfc(x). 

  14. What is a Bessel function? 

  15. What is the finite difference formula used for?  Explain with a figure the finite differences formula for:

  • Forward difference. 

  • Backward difference. 

  • Central difference (for first and second order). 

  1. Describe briefly the step by step procedure of solving a PDE through:

  • Method of lines. 

  • Separation of variables. 

  • Similarity transformation.

II. Thermodynamics:

  1. Explain in words the first law of thermodynamics. 

  2. Explain in words the second law of thermodynamics for: 

  3. A reversible process.

  4. An irreversible process. 

  5. Draw the diagram for a heat engine and for a refrigerator and explain how it relates to the second law. 

  6. Draw a P-T diagram for a pure component and identify the one, two, and three phase regions. 

  7. Draw a P-V diagram for a pure component and identify the one, two, and three phase regions. 

  8. Draw a P-x-y diagram at constant T for a binary system.  Identify the one and two-phase regions.  From this diagram obtain the corresponding x-y diagram.  Explain. 

  9. Same as (6) starting from a T-x-y diagram at constant P. 

  10. Define an azeotrope.  Draw P-x-y, T-x-y and x-y diagrams for a binary system that forms azeotropes. 

  11. Write the equilibrium equations for a VLE binary system.  Explain how you would model the vapor and liquid phases for a (an): 

  12. System at low pressure. 

  13. System at high pressure. 

  14. Liquid containing a polymer. 

  15. Aqueous salt solution. 

  16. Write the equilibrium equations for a LLE binary system.  Draw the T-x diagram for a:

  17. Partial miscibility with an upper critical solution point. 

  18. Total miscibility at low temperatures, partial miscibility at intermediate temperatures, and total miscibility at high temperatures. 

  19. In a P-T diagram for a pure component, identify the curves of saturation pressure for a liquid and for a solid. 

  20. Explain the physical meaning of fugacity and fugacity coefficient.  What are the units for these two quantities?  What is the value of the fugacity and fugacity coefficient for a single component at low pressures? 

  21. Write the Gibbs phase rule and calculate the number of degrees of freedom for a single component: 

  22. Along the vaporization curve. 

  23. At the triple point. 

  24. At the critical point.  Does the Gibbs phase rule apply at the critical point?  Explain your answer. 

  25. Chemical potential: 

  26. Define with an equation and give units. 

  27. Explain its physical meaning. 

  28. Is there a unique definition?  Explain.  

  29. Explain the physical meaning of an activity coefficient and describe a situation where you would use one.  Provide the simplest model for a liquid phase activity coefficient. 

  30. Define the Gibbs free energy and the Helmholtz free energy.  Why are they called 'free’ energies? 

  31. What is osmotic pressure? Give an example of an application that takes advantage of the osmotic pressure. 

  32. Define and give an example of a partial molar property. 

  33. In electrolyte solutions, why is it necessary to define a “mean” activity coefficient?

  34. Draw a P-V phase diagram for a pure component and identify regions of supersaturated vapor and compressed liquid.

III. Fluid Flow:

  1. Explain in words the meaning of the continuity equation.  Describe a physical situation and state in words how you would apply the continuity equation.

  2. Explain in words the meaning of the Navier-Stokes equation.  Describe a physical situation and state in words how you would apply the continuity equation. 

  3. In simple terms, what is a Newtonian fluid and a non-Newtonian fluid?  Give examples of both. 

  4. Write the stress tensor for a Newtonian fluid. 

  5. Explain in words Newton’s second law of motion.  Does this apply to all fluids, whether Newtonian or not?  Explain. 

  6. What is the difference between a partial derivative and a material derivative? 

  7. For the following cases, simplify the continuity equation and the equation of motion (in the appropriate coordinate system), write the boundary conditions, and sketch the velocity profiles and the shear stress profiles.  Clearly state what you are assuming and justify all assumptions.  For each case, consider water and air.  

  8. Unidirectional flow between infinite parallel plates due only to the movement of one of the plates. 

  9. Unidirectional flow between infinite parallel plates due only to a pressure difference. 

  10. Unidirectional flow inside a circular pipe due to a pressure difference. 

  11. Unidirectional flow outside a cylinder rotating in a large pool of fluid. 

  12. Unidirectional flow outside a sphere rotating in a large pool of fluid. 

  13. Flow near an infinite rotating cylinder. 

  14. Falling film down an incline plane. 

  15. What is vorticity?  Give examples of flows with and without vorticity. 

  16. What is a stream function?  Define a stream function for the case when there is flow only in the x and y directions (Cartesian coordinates). 

  17. What is a boundary layer?  Simplify the continuity equation and the equation of motion for the laminar boundary layer of a flat plate placed parallel to a fluid moving at a uniform velocity. 

  18. How does method of separation of variables work?  Give an example of a flow where this method is used to solve the equations of fluid mechanics. 

  19. How does method of similarity solutions work?  Give an example of a flow where this method is used to solve the equations of fluid mechanics. 

  20. Describe how the flow develops when a pressure gradient is applied to a fluid that was previously stationary inside a pipe. 

  21. For a steady state situation (no change in time), describe how the velocity profile changes along a pipe starting from its entrance, which is connected to a large reservoir from which the fluid enters due a pressure difference. 

  22. Why is the stress tensor symmetric?  Does it have to be symmetric?  Explain. 

  23. Describe the assumptions behind the “lubrication approximation”.  Describe a flow situation in which the analysis is simplified using this approximation. 

  24. How would you solve the problem of fluid flow in a tapered tube under a pressure gradient?

  25. How would you solve the problem of the development of the thickness of a fluid film falling down an inclined surface?

[Site maintained by Vijay A. Sethuraman; Date last updated: March 10, 2007]