- 1.1 What Is Mass Transfer?
- 1.2 Preliminaries: Continuum and Concentration
- 1.3 Flux Vector
- 1.4 Concentration Jump at Interface
- 1.5 Application Examples
- 1.6 Basic Methodology of Model Development
- 1.7 Conservation Principle
- 1.8 Differential Models
- 1.9 Macroscopic Scale
- 1.10 Mesoscopic or Cross-Section Averaged Models
- 1.11 Compartmental Models
- Summary
- Review Questions
- Problems

## Review Questions

**1.1** What is meant by a concentration jump?

**1.2** What is meant by the continuum assumption and what are its implications in model development?

**1.3** Indicate some situations where the continuum models are unlikely to apply.

**1.4** Give an example of a system in which the total concentration is (nearly) constant.

**1.5** Give an example of a system in which the mixture density is nearly constant.

**1.6** Can average molecular weight be a function of position?

**1.7** Which information is missing in the differential models based on the continuum assumption?

**1.8** Why are constitutive models needed in the context of differential models?

**1.9** Does the Fick’s law apply universally to all systems?

**1.10** Write a form of Fick’s law using partial pressure gradient as the driving force.

**1.11** What is meant by the invariant property of the flux vector?

**1.12** The combined flux is partitioned into the sum of the convection flux and the diffusion flux. Is this partitioning unique?

**1.13** State the units of the gas constant if the pressure is expressed in bar instead of Pa, (ii) if expressed in atm.

**1.14** Express the dissolved oxygen concentration in Example 1.1 in parts per million (ppm).

**1.15** What is a macroscopic-level model? Which information needs to be added in such a model in addition to the conservation principle?

**1.16** How is the mass transfer coefficient defined? Why is it needed?

**1.17** What is meant by a cross-sectional average concentration? What is a cup mixing or the bulk concentration?

**1.18** Which assumptions are involved in a plug flow model?

**1.19** Which assumptions are involved in a completely backmixed model?

**1.20** Which additional closure is needed for mass transport in turbulent flow? Why?

**1.21** What is an ideal stage contactor? How do you correct the model if the stage is not ideal?

**1.22** What is the dispersion coefficient and where is it needed?