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GUJARAT TECHNOLOGICAL UNIVERSITY
BE — SEMESTER - IV EXAMINATION — WINTER 2017
Date: 29/11/2017
Subject Name: Fundamental Chemical Engineering Calculations & Stoichiometry
Time: 02.30PM to 05.00PM
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Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
Q.1 (a) Classify the material balance. Discuss the various methods involved for solving material balance problems without chemical reactions. 07
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(b) The gaseous reaction A ? 2B + C takes place isothermally in a constant pressure reactor. Starting with a mixture of 75% A and 25% inerts (by volume), in a specified time the volume doubles. Calculate the conversion achieved. 07Q.2 (a) The diameter and height of a vertical cylindrical tank are 4 ft and 6 ft 6 inch respectively. It is full up to 80% height with carbon tetrachloride, the density of which is 1.6 kg/l. Find the mass in kilograms and pounds. 07
(b) The conductance of a fluid-flow system is defined as the volumetric flow rate, referred to a pressure of one torr (133.322 Pa). For an orifice, the conductance C can be computed from
C = 894 A / (T/M)1/2
Where A = area of opening, ft2; T = Temperature, °R; M = Molecular Weight
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Convert the empirical equation into SI units. 07Q.3 (a) OR
Discuss about recycling and bypassing operations with their importance. 07
(b) With a typical example, explain: the terms: Conversion, Yield, Selectivity, Limiting component and Excess component. 07
Q.3 (a) Differentiate between: (i) Sensible heat and latent heat (ii) Endothermic and exothermic reactions (iii) intensive property and extensive property. 07
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(b) ORA gas mixture has following composition by volume: CH4: 40%, C2H6: 35%, C3H8: 25%. Find the average molecular mass of the gas mixture. Also find the density of mixture in kg/m3 at STP. 07
Q.4 (a) The average molecular mass of a flue gas sample is calculated by two different engineers. One engineer uses the correct molecular mass of 28 for N2 and determines the average molecular mass to be 30.08, the other engineer, using an incorrect value of 14, calculates the average molecular mass to be 18.74. Calculate the volume % of N2 in the flue gases. If the remaining components of the flue gases are CO2 and O2, calculate the volume % of each of them. 07
(b) Find the heat that must be transferred to heat a mixture of 25 mol% N2 and 75 mol% H2 from 298 K to 473 K flowing at a rate of 1.5 kmol/h. Heat capacity data: Cp (kJ/kmol.K) = a + bT + cT2 + dT3
Gas a b x 103 c x 106 d x 109
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N2 29.59 -5.41 13.18 -4.97H2 28.61 1.02 -0.15 0.77
Total Marks: 70
Q.4 (a) OR
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Ferric sulphide ore containing 85% FeS2 and 15% inert gangue is roasted with dry air. Analysis of the gas leaving the reactor shows 11.2% SO2, 7.4% O2 and 81.4% N2. Calculate the percentage of excess air used. What percentage of the sulphur in the ore is converted to SO3? Assume that the reaction proceeds in the following manner.4FeS2(s) + 11O2(g) ? 2Fe2O3(s) + 8SO2(g) 07
(b) OR
A spent lye sample contains 9.6% glycerol and 10.3% NaCl salt. It is concentrated at the rate of 5000 kg/h in a double effect evaporator until the final solution contains 80% glycerol and 6% salt. 45% glycerol is lost by entrainment. All the percentage are by mass. Determine:
(1) the evaporation taken place in the system
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(ii) the amount of salt crystallized out from the evaporator 07Q.5 (a) Pure methane is heated from 303K to 523K at atmospheric pressure. Calculate the heat added per kmol of methane using the following Cp data.
Cp=a+bT +cT2+dT3
Where a =19.2494, b x 10-3=52.1135, c x 10-6=11.973, d x 109 =-11.3173 07
(b) Define the following unit operations with suitable diagram and example: distillation, crystallization and evaporation. 07
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Q.5 (a) Define the following terms with supporting equations: (i) Absolute humidity (ii) Relative humidity (iii) Humid heat 07
(b) OR
It is required to make 1000 kg mixed acid containing 60% H2SO4, 32% HNO3 and 8% water by blending (i) spent acid containing 11.3% HNO3, 44.4% H2SO4 and 44.3% H2O, (ii) aqueous 90% HNO3 and (iii) aqueous 98% H2SO4. All percentage are by weight. Calculate the quantities of each of the three acids required for blending. 07
The dry bulb temperature & dew point of ambient air were found to be 302 K & 291 K respectively. The barometer reads 100 kPa, calculate : a) the absolute molal humidity, b) the absolute humidity, c) % RH, d) % saturation, e) humid heat, and f) humid volume.
Data : Vapour pressure of water at 291 K =2.0624 kPa
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Vapour pressure of water at 302 K = 4.004 kPa 07--- Content provided by FirstRanker.com ---
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