Appendix: Solutions to Chapter Exercises ◾  123
Exercise 6.5
Using Equation 6.6, N OL = (1) (Ln 3)/(1 − 1/3) = 1.65 liquid
phase mass transfer units.
Exercise 6.6
Using Equation 6.1, S = (1/350) (1.1/0.1) = 0.0314
and Equation 6.8, N OG = {Ln[(5000/1)(1 − 0.0314) + 0.0314]}/
{1 − 0.0314} = 8.76 gas phase mass transfer units.
Exercise 7.1
DNS = 0
Failure rate = ½
(½)(21) = 10 or 11 samples per week would be out of spec.
Exercise 7.2
Failure rate of 1/790 would require DNS = 3.0 sigma

0.3% − (3.0)(.025) = 0.3 − 0.075 = 0.225% ethanol

Exercise 7.3
The MRT setpoint should be raised to increase toluene concentration and reduce the benzene concentration left in
the bottoms.