1. Home work Assignment No # 1 ChE 333: Mass Transfer Department of Chemical and Materials Engineering Faculty of Engineering King Abdulaziz University Jeddah, KSA Name of the student : Student Number : Comments: Instructor : Dr Sharif Zaman Submission date : 18-9-2015 Q1[25]Q2[25]Q3 [25]Q4[25] Q1 Q2 Q3 Q4

2. Question 1 : A mixture 1.0 mol % O 2 (species A) in a helium carrier gas (species B) enters the micro scale chamber. The chamber consists of a channel that is 5.0 mm (microns) in diameter. The total system pressure within the chamber is 300 Pa, which is very small. The chamber temperature is maintained at 100 o C. The molecular weight of oxygen is 32 g/g mol and helium is 4.0 g/g mol. a. What is the molar concentration of oxygen gas at the entrance to the micro chamber? b. What is the effective diffusion coefficient of O 2 (D Ae ) within the micro chamber?

3. Question 2 : Benzene (species A) is often added to ethanol to denature the ethanol (species B). Estimate the liquid-phase diffusion of benzene in ethanol and ethanol in benzene at 288 K by (a)The Wilke–Chang equation and (b)The Scheibel equation. (c)Does D AB = D BA ?

4. Question 3: An absorption tower has been proposed to remove selectively two pollutants, hydrogen sulfide (H 2 S) and sulfur dioxide (SO 2 ), from an exhaust gas stream containing H 2 S-3 Vol% SO 2 -5 vol% N 2 - 92 vol% Estimate the diffusivity of hydrogen sulfide in the gas mixture at 350 K and 1.013 x 10 5 Pa: The critical temperature (T C ) of H 2 S is 373.2 K and the critical volume (V C ) of H 2 S is 98.5 cm 3 /mol.

5. Question 4: Steam reforming of hydrocarbons is one way to make hydrogen gas (H 2 ) for fuel cells. However, the product gas contains H 2 contaminated with carbon monoxide (CO), which must be further enriched in H 2 in order for the fuel cell to work better. It is desired to separate a mixture of CO and H 2 using a microporous ceramic membrane. The average pore diameter of the porous membrane material is 15 nm, and the void fraction e= 0.10. The system operates at 5.0 atm total system pressure and 400 O C. Determine the effective diffusion coefficient of CO in the gas mixture within the microporous membrane. Is Knudsen diffusion important? (Calculate Knudsen number) Assumption: You may assume that the CO is dilute in the gas mixture.