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Unformatted text preview: Chemical Engineering 140 September 10, 2008
Problem Set #3 11. Given on a previous midterm.
To test the dynamic response of an inline or flow-through spectrophotometer, it is helpful
to use an exponential dilution flask upstream of the photometer. The effluent from a small
continuous, stirred tank (i.e., a flask) is fed to the photometer. Initially, the tank is filled
with a dilute dye at concentration C. Then, clear solvent (i.e., containing no dye) is fed to
the flask while maintaining the same inlet and outlet flow rates. If the transmitted
absorbance measured by the photometer (i.e. minus the logarithm of the intensity) is linear
with dye concentration, find an expression for the spectrophotometer absorbance, A, in
terms of a steady flow rate Q, and the steady volume of liquid in the flask, V. Explain why
the device is called exponential dilution flask and why it is useful in testing the dynamic
behavior of the spectrophotometer 12. 32.5
15. 32.18 For the instantaneous initial flow rate with the small tank evacuated, use
0.20 kg mol/hr (not 0.091). For the initial pressure in Tank 1, use 700 kPa (not 690 kPa). ...
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This note was uploaded on 02/05/2010 for the course CHM ENG 140 taught by Professor Radke during the Fall '08 term at University of California, Berkeley.
- Fall '08