GTU BE/B.Tech 2019 Winter Question Papers || Gujarat Technological University
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GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- III (New) EXAMINATION — WINTER 2019
Subject Code: 3130508 Date: 3/12/2019
Subject Name: Material & Energy Balance Computation
Time: 02:30 PM TO 05:00 PM Total Marks: 70
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Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
| Marks | ||||
|---|---|---|---|---|
| Q.1 (a) A mixture of nitrogen and carbon dioxide at 298 K and 101.325 kPa has an average molecular weight of 31. Calculate the partial pressure of nitrogen. | 03 | |||
| (b) The flow rate of water through a pipe is reported as 20 ft3 / min. Convert the volumetric flow rate into the mass flow rate in kg/sec. Density of water is 1 gm/cc. | 04 | |||
| (c) Discuss the importance of recycling and bypassing operation | 07 | |||
| Q.2 (a) A sample of well water contains 140 gm/m3 Ca+ ions and 345 gm/m3 Na+ ions. Express the hardness of the water sample in terms of equivalent of CaCO3 in gm/m3. (Atomic weight of Ca = 40, Na = 23,C=12and O =16) | 03 | |||
| (b) Describe the material balance of drying operation. | 04 | |||
| (c) A solution of NaCl in water contains 15 % NaCl (by mass) at 335 K. The density of the solution is 1.127 kg/lit. Determine the molarity, normality and molality of the solution. | 07 | |||
| OR | ||||
| (c) A gaseous mixture has the following composition by volume. SO2 = 6 %, O2 = 9%, CO = 1.5% and CO2 = 4.5 % and remaining is nitrogen. Calculate (a) the density of gas mixture at a temperature of 425 K and at a pressure of 202.65 kPa g and (b) Composition by weight. | 07 | |||
| Q.3 (a) Describe the material balance of liquid — liquid extraction. | 03 | |||
| (b) In a paper mill, a wash liquor containing 3% (by weight) solid is concentrated in an evaporator to yield a lye containing 30% (by weight) solids. Calculate the quantity of water evaporated per 100 kg of feed? | 04 | |||
| (c) A coke is known to contain 90% carbon and 10% non combustible ash by weight. (a) Calculate the moles of oxygen are theoretically required to burn 100 kg of coke completely? (b) If 50 % excess air is supplied calculate the analysis of gases at the end of combustion. | 07 | |||
| OR | ||||
| Q.3 (a) List out the classification of material balance problems. | 03 | |||
| (b) The orsat analysis of a flue gas is CO2 = 12.7 %, O2 = 7.1% N2 = 80.2 %. Determine the percentage excess air used in combustion. The nitrogen present in the flue gas is contributed by air only. | 04 | |||
| (c) In a production of chlorine gas by oxidation of hydrochloric acid gas, air is used 30 % in excess of that theoretically required. Based on 4 kmol HCI, Calculate; (a) The weight ratio of air to HCI gas in feed. (b) If oxidation is 85 % complete, calculate the composition off product stream on mole basis. | 07 | |||
| Q.4 (a) Calculate the standard heat of reaction of the following reaction using std. heat of formation data. CH1.8 + 8O2 ? 5CO2 + 6H2O | 03 | |||
| Component | ?Hf = kJ/mol @25°C | |||
| C5H12 | -173.49 | |||
| CO2 (g) | -393.51 | |||
| H2O (g) | -285.83 | |||
| (b) A feed to a continuous fractionating column (Distillation column) analyses by weight 28 % benzene and 72 % toluene. The analysis of the distillation shows 52 % (weight) benzene and 5 % (weight) benzene was found in the bottom product. Calculate the amount of distillation and bottom product per 1000 kg of feed per hour. Also calculate the recovery of benzene. | 04 | |||
| (c) Pure CO is mixed with 100 % excess air and burnt. Only 80% of CO is burns. The reactants are at 100 °C and the products are at 300 °C. Estimate the amount of heat added or removed per kmol of CO fed to the reactor. Data: Mean molal specific heat between 25 °C and T °C in kJ/kmol K are as follows. | 07 | |||
| Gas | T=100°C | T =300°C | ||
| CO | 29.22 | 30.61 | ||
| CO2 | - | 43.77 | ||
| O2 | 29.64 | 43.77 | ||
| N2 | 29.17 | 29.66 | ||
| Standard heat of formation at 25 °C are: CO =-110524 kJ/kmol and CO2 = -393514 kJ/kmol | ||||
| OR | ||||
| Q.4 (a) Calculate the enthalpy change (std. heat of reaction) between reactants and products if both are at 298.15 K and if 10 mol of formaldehyde is produced according to the following reaction. CH4(g) +O2(g) ? HCHO(g) + H2O(g) | 03 | |||
| Component | ?HCo = kJ/mol @25°C | |||
| CH4(g) | -890.65 | |||
| HCHO | -563.46 | |||
| (b) The spent acid from a nitrating process contains 15% HNO3, 65% H2SO4 and 20% H2O by weight. This acid is to be concentrated to contain 25 % HNO3 and 58 % H2SO4 by addition of concentrated sulphuric acid containing 93% H2SO4 and concentrated nitric acid containing 90% HNO3. Calculate the weights of spent acid, concentrated sulphuric acid and concentrated nitric acid that must be combined to obtain 100 kg of the desired mixture. | 04 | |||
| (c) A gas mixture has the following composition on mole basis. CH4 = 84, C2H6 = 13% and N2 = 3%. Calculate the energy to be added to heat the 15 kmol of gas mixture from 298 K to 523 K using heat capacity data given below. Cpo =a +bT + cT2 +dT3 where Cp is in kJ/kmol K or J/mol K | 07 | |||
| Component | a | b x103 | c x106 | d x109 |
| CH4 (g) | 19.25 | 52.11 | 11.97 | -11.32 |
| C2H6 (g) | 5.41 | 178.19 | -67.38 | 8.72 |
| N2 | 29.59 | -5.41 | 13.18 | -4.97 |
| Q.5 (a) Define. (a) Adiabatic flame temperature (2) Latent heat (c) Excess air requirement. | 03 | |||
| (b) A liquid fuel is found to contain 83% C, 15% hydrogen and 2% Sulphur. Calculate the net calorific value (NCV) of liquid sample at 298 K. Data: Gross calorific value of fuel at 298 K is 45071 klJ/kg of liq fuel. Latent heat of water vapour at 298K =2442.5 kJ/kg. | 04 | |||
| (c) Discuss classification of fuels and define calorific values of fuels. | 07 | |||
| OR | ||||
| Q.5 (a) Define. (1) Heat capacity (2) Calorie (3) Humidity | 03 | |||
| (b) Calculate the calorific value at 298K of a sample of fuel oil having C/H ratio of 9.33 (by weight) and containing sulphur to the extent of 1.3 % by weight. Data: The Gross calorific value (GCV) of fuel oil at 298 K = 41785 kJ/kg. Latent heat of water vapour (25.°C) = 2442.5 kl/kg | 04 | |||
| (c) Discuss Ultimate analysis and proximate analysis of coal. | 07 | |||
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