Mass Transfer – Multiple Choice Questions (MCQs)

1. 25. What is the 'mass transfer coefficient'?

   • A. A measure of the rate of mass transfer per unit area per unit concentration difference
   • B. A measure of diffusion
   • C. A measure of viscosity
   • D. A measure of thermal conductivity

2. 26. What is the unit of the overall mass transfer coefficient (K_G or K_L)?

   • A. mol/(m²·s)
   • B. m/s
   • C. kg/(m³·s)
   • D. J/(m²·s·K)

3. 27. What is the driving force for mass transfer in distillation?

   • A. Temperature difference
   • B. Pressure difference
   • C. Relative volatility
   • D. Density difference

4. 28. What is relative volatility (α)?

   • A. A measure of the ease of separation of two components by distillation
   • B. The ratio of vapor pressures
   • C. The ratio of densities
   • D. The ratio of viscosities

5. 29. What is the minimum number of theoretical stages in a distillation column at total reflux?

   • A. Zero
   • B. One
   • C. Infinity
   • D. Depends on the feed composition

6. 30. What is the minimum reflux ratio in a distillation column?

   • A. The minimum amount of reflux required for a given separation
   • B. The maximum amount of reflux allowed
   • C. The ratio of product to feed
   • D. The ratio of reboiler duty to condenser duty

7. 31. What is the operating line for the enriching section of a distillation column?

   • A. y = (R/(R+1))x + (x_D/(R+1))
   • B. y = x
   • C. y = (L/V)x + (D/V)x_D
   • D. y = x_D

8. 32. What is the operating line for the stripping section of a distillation column?

   • A. y = (R/(R+1))x + (x_D/(R+1))
   • B. y = x
   • C. y = (L̄/V̄)x - (B/V̄)x_B
   • D. y = x_B

9. 33. What is the q-line in distillation?

   • A. A line representing the feed condition on a McCabe-Thiele diagram
   • B. A line representing the boiling point
   • C. A line representing the dew point
   • D. A line representing the equilibrium curve

10. 34. What does q represent in the q-line equation?

    • A. The fraction of liquid in the feed
    • B. The fraction of vapor in the feed
    • C. The total enthalpy of the feed
    • D. The heat capacity of the feed

11. 35. What is the McCabe-Thiele method used for?

    • A. Graphical determination of theoretical stages in distillation
    • B. Calculation of heat transfer coefficients
    • C. Design of heat exchangers
    • D. Estimation of fluid flow rates

12. 36. What is the concept of 'overall mass transfer coefficient'?

    • A. Combines individual mass transfer coefficients into a single term for interphase mass transfer
    • B. Separates individual mass transfer coefficients
    • C. Only for single-phase mass transfer
    • D. Not relevant for interphase mass transfer