Semester 1, Academic Year 2001/2002 Section B
Question 11
A 100 g-mole ethanol-water mixture consisting of 60 wt% ethanol (MW = 46) and 40 wt% water (MW = 18) is subjected to simple distillation. At the end of the process, the residual in the still contains 30 wt% ethanol and the distillate obtained contains 80 wt% ethanol. Calculate the amount of distillate (in g-mole) obtained.
( 8 marks )
Question 12
The equilibrium data for hexane-octane at 1 atm are given in the table below.
Determine the relative volatility for the mixture at 93.3 oC and discuss if the mixture can be effectively separated by distillation under 1 atm.
( 8 marks )
Question 13
With the aid of an appropriate diagram, briefly discuss the characteristics of a valve tray and explain how it operates in response to varying vapour flow rate.
( 8 marks )
Question 14
Oxygen (component-A) is diffusing through a non-diffusing carbon dioxide (component-B) under steady-state conditions. The total pressure is 1 x 105 Pa, and the temperature is 0 oC. The diffusion path is 5.0 mm. The partial pressures of oxygen at the 2 ends of the diffusion path are 12,000 Pa and 5,000 Pa respectively. The diffusivity of the mixture is 1.87 x 10-5 m2/s. Calculate the molar flux of O2 in the mixture.
Given R = 8314 (m3.Pa)/(kg-mole.K) and the following molar flux equation:
( 8 marks )
Question 15
(a) Name 3 types of commercially available packing.
( 3 marks )
(b) State 5 desirable characteristics of packing.
( 5 marks )