THE UNIVERSITY OF TRINIDAD & TOBAGO FINAL EXAMINATION APRIL 2014 PLEASE READ ALL INSTRUCTIONS CAREFULLY BEFORE YOU BEGIN THIS EXAMINATION

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1 THE UNIVERSITY OF TRINIDAD & TOBAGO FINAL EXAMINATION APRIL 2014 ourse ode and Title: MATERIAL BALANE Programme: NETD HEMIAL ENGINEERING Date and Time: Tuesday 22 nd April 2014, 9.00 a.m noon Duration: 3 HOURS PLEASE READ ALL INSTRUTIONS AREFULLY BEFORE YOU BEGIN THIS EXAMINATION Instructions to andidates 1. This paper has 10 pages and 5 questions. 2. You are required to answer ALL questions. You are required to return the Question paper and Data booklet with the Answer script to the Invigilator before leaving the Examination room. Key Examination Protocol 1. Students please note that academic dishonesty (or cheating) includes but is not limited to plagiarism, collusion, falsification, replication, taking unauthorised notes or devices into an examination, obtaining an unauthorised copy of the examination paper, communicating or trying to communicate with another candidate during the examination, and being a party to impersonation in relation to an examination. 2. The above mentioned and any other actions which compromise the integrity of the academic evaluation process will be fully investigated and addressed in accordance with UTT s academic regulations. 3. Please be reminded that speaking without the Invigilator s permission is NOT allowed. University of Trinidad and Tobago Page 1 of 10

2 ANSWER ALL QUESTIONS 1. a) 6 LiH + 2 Bl 3 B 2 H Lil Diborane, B 2 H 6, a possible rocket propellant, can be made by using Lithium If you mix 400 g of LiH with 1175 g of Bl 3, you recover 112.0g of B 2 H 6. Determine: i) The limiting reactant (5 marks) ii) The percent excess of the reactant present in excess. (3 marks) iii) The degree of completion of the reaction. (2 marks) R.A.M.: B 11, Li 7, l 35.5, H 1 b) A sample of gas is analysed at 1 atm pressure and is found to have the following composition by mass: opy and complete the table. omponent Mass Percent O 9 O 2 22 N 2 56 H 2 4 H 2 O 9 Mass (kg) R.M.M. Number of kmol Mole fraction i) What is the basis of calculation? (1 mark) ii) alculate the average molecular mass of the gas. (7 marks) iii) Determine the molar composition of the sample (2 marks) University of Trinidad and Tobago Page 2 of 10

3 2. a) A gas flowing in a pipeline at a rate of 2240 m 3 /h as measured at (s.t.p) standard temperature and pressure. alculate the actual volumetric flow rate if the pressure in the pipeline is 14 atmospheres and the temperature is 175 o. Assume that the critical temperature is 280 K and the critical pressure is 20 atmospheres. (10 marks) V r P V RT T T R PR T P P P V znrt where z is the compressibility factor b) arbon dioxide (O 2 ) is to be stored in a steel tank at190 K. The tank has a volume of 10.4 m 3 and you want to store 440 kg of O 2 in it. Using the Van der Waals equation of state, determine the pressure that the O 2 will exert. (10 marks) a P + ( v b) RT v 2 wherev is the molar volume 2 27R T a 64 P RT b P For O 2 : Pc 72.9 atm Tc K University of Trinidad and Tobago Page 3 of 10

4 3. a) alculate the molar composition of stream 1. (5 marks) b) 9400 kg/ h of a 2 H 5 OH/ H 3 OH mixture is to be separated in a distillation column. The feed is 40.0 mole % 2 H 5 OH and the distillate has 90.0 mole % H 3 OH and 80 % of the H 3 OH in the feed is to be recovered as distillate. i) alculate the molar flow rate of the feed. (5 marks) ii) alculate the molar flow rate of the distillate (3 marks) iii) Determine the molar composition of the bottom product. (7 marks) University of Trinidad and Tobago Page 4 of 10

5 4. a) Determine the recycle ratio ( F R ) for the process shown below. (15 marks) b) Determine the value of n and 1 n 2. (5 marks) 125 kmol 2 H 6 / min REATOR 45 kmol H 2 /min n (kmol 1 2 H 4 /min) n (kmol 2 2 H 6 /min) ` University of Trinidad and Tobago Page 5 of 10

6 5. a) The latest weather report includes the following statement: The temperature is 32 o, barometric pressure is 1 bar and the relative humidity is 75 %. Using this information, estimate i) the mole fraction of water vapour in the air (4 marks) ii) the dew point (4 marks) iii) molal humidity and (2 marks) iv) absolute humidity. (2 marks) Use 1 bar 100 kpa b) A mixture of air and benzene contains 10-mole % benzene at 38 o and 790 mm Hg pressure absolute. The vapour pressure of benzene is given as log 10 p T where p is the vapour pressure in mm Hg and T is in o. What is the dew point of the mixture? (8 marks) END OF EXAM University of Trinidad and Tobago Page 6 of 10

7 Universal gas constant R J mol or K 3 Pa m mol K kj kmol or K kpa L mol K atm L mol K mm Hg mol K cm 3 atm mol K Molal humidity p vapor p total p vapor Relative Humidity p vapor p x 100 vapor P y P i where P is the system pressure i Humidity x Molal Humidity University of Trinidad and Tobago Page 7 of 10

8 ONVERSION FATORS 1000 L 1 m 3 MASS ONVERSION FATORS 1 lb x 10 2 g 1 kg 1000 g 1kg 2.2 lb m PRESSURE ONVERSION FATORS 1 atm Pa kpa 1 atm 760 mm Hg 1 atm bar TEMPERATURE ONVERSION FATORS T (K) T ( o ) T ( o F) 1.8 ( o ) + 32 T ( o ) (T ( o F) 32) x 9 5 University of Trinidad and Tobago Page 8 of 10

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