Code No: RR210803Set No. 1 II B.Tech I Semester Supplementary Examinations, February 2007 MATERIAL & ENERGY BALANCE (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Aqueous solution of triethanolamine (TEA) i.e N(CH2 CH2 OH)3 , contains 50% TEA by weight. Find the molarity of the solution if the densiy of the solution is 1.05 kg/L. (b) The concentration of CO2 is measured to be 0.206 kmol per kmol monoethanolamine (MEA) in a 20% (by weight) aqueous MEA solution. Assuming the density of the solution to be nearly 1.0 kg/L, find the concentration of CO2 as weight % and mole % in the solution. The chemical formula of MEA is NH2 CH2 CH2 OH. [8+8] 2. (a) A gas mixture contains 0.274 kg mole of HCl, 0.337 kg mole of nitrogen and 0.089 kg mole of oxygen. Calculate i. The volume occupied by the mixture and ii. Its density in kg/m3 at a pressure of 2000 mm Hg and temperature of 300 C. (b) Write about the applications of ideal gas law. [8+8] 3. Write short notes on: (a) Cox chart and its applications. (b) Duhrings chart and its application. (c) Critical properties. (d) Reduced conditions. [4×4] 4. (a) Describe adiabatic vaporization with an example. What type of industrial operations are carried out using adiabatic vaporization. (b) What is the minimum number of cubic meters of dry air at 200 C and 100 kPa that are necessary to evaporate 6 kg of ethyl alcohol if the total pressure remains constant at 100 kPa ? Assume that the air is blown through the alcohol to evaporate it in such a way that the exit pressure of the air-alcohol mixture is at 100 kPa. Vapor pressure of ethyl alcohol at 200 C =5.93 kPa. [8+8] 5. (a) A solution of potassium dichromate in water contains 15% by weight of K2 Cr2 O7 . Calculate the amount of K2 Cr2 O7 crystals that can be produced from 1500 kg of solution if 700 kg of water is evaporated and the remaining solution is cooled to 293K. The solubility of K2 Cr2 O7 at 293K is 115 kg per 1000 Kg water. 1 of 2 Code No: RR210803 Set No. 1 (b) The NH3- air mixture containing 0.2 kg NH3 per kg air enters into an absorption system where ammonia is absorbed in water. The gas leaving the system is found to contain 0.004 kg NH3 per kg of air. Find the percentage recovery of ammonia. [8+8] 6. What will be the yield of Glauber salt (Na2 SO4 .10H2 O) if a pure 32% solution is cooled to 200 C without any loss due to evaporation. Solubility of Na2 SO4 in water at 200 C is 19.4 kg per 100 kg water. [16] 7. (a) Write about the following: i. Kopp’s rule. ii. Trouton’s rule. iii. Kistyakowsky equation for non-polar liquids. (b) Calculate the heat of vaporization in cal/g of carbon tetrachloride at its normal boiling temperature (76.70 C) by the following methods: i. From the equation of Kistyakowsky ii. Trouton’s rule [8+4+4] 8. (a) Explain the usefulness of the enthalpy-concentration diagrams. (b) Chlorinated diphenyl is heated from 40 to 800 C at the rate of 4000 kg/hr in an indirectly fired heater. The specific heat of the fluid in the temperature range is given by Cp = 0.275 + 0.35 x 10−3 t (kcal/kg 0 C) where t is in 0 C. Calculate the heat to be supplied to the fluid in the heater. [8+8] ⋆⋆⋆⋆⋆ 2 of 2 Code No: RR210803 Set No. 2 II B.Tech I Semester Supplementary Examinations, February 2007 MATERIAL & ENERGY BALANCE (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) In the decomposition of KClO3 , 2KClO3 —–→ 2KCl +3O2 , i. Calculate the amount of oxygen that evolves on decomposition of 12.9 gm of KClO3 . ii. Calculate the amount of KClO3 for evolution of 5 gm of oxygen. (b) A solution of caustic soda in water contains 20% NaOH by weight at 333K. The density of the solution is 1.196 kg/L. Find the molarity, normality and molality of the solution. [4+4+8] 2. (a) An ideal gas mixture at 10 bar absolute and 2000 C in a 100 m3 tank contains 50 mole% H2 and 50 mole% N2 . What is the partial pressure of H2 ? What is the pure-component volume of H2 ? (b) The gas acetylene is produced according to the following reaction by treating calcium carbide with water: CaC2 + 2 H2 O C2 H2 + Ca(OH)2 . Calculate the number of hours of service that can be derived from one kg of carbide in an acetylene lamp burning 0.5 m3 gas per hour at a temperature of 250 C and 750 mm Hg pressure. [8+8] 3. (a) What are critical properties? Write about estimation of critical properties of organic substances and inorganic substances. (b) A mixture of ethyl acetate vapor and air has a relative saturation of 50% at 300 C and a total pressure of 740 mm Hg. Calculate the analysis of vapor and percentage molar saturation, the vapor pressure of ethyl acetate at 300 C is 119 mm Hg. [8+8] 4. (a) Describe the humidity chart with its application. (b) A mixture of air and benzene is found to have a 50% relative saturation at 270 C at an absolute pressure of 110 kPa. What is the mole fraction of benzene in the air. The vapor pressure of benzene at 270 C is 103.5 mm Hg. [8+8] 5. A wet organic pigment containing 35 % by weight of CCl4 is to be dried to 5% by weight of CCl4 . The drier is to operate adiabatically with fresh plus recycle air at 1000 C and 101325 N/m2 pressure. Having a CCl4 dew point of 150 C and discharging air with a CCl4 dew point of 250 C. The capacity of the drier is 200 kg of bone dry solid per hour. The vapor pressure of CCl4 at 150 C is 7590N/m2 and at 250 C is 15300 N/m2 . Calculate (a) kg of fresh air to be supplied per hour. 1 of 2 Code No: RR210803 (b) The recycle ratio. Set No. 2 [8+8] 6. A crystalliser is charged with 7500 kg of an aqueous solution at 377K, 29.6% (by weight) of which is anhydrous sodium sulfate .The solution is cooled. During the cooling operation, 5% of the initial water is lost by evaporation. As a result, crystals of Na2 SO4 .10H2 O crystallize out. If the mother liquor is found to contain 18.3% (by weight) anhydrous sodium sulfate, calculate the yield of crystals and the quantity of mother liquor. [16] 7. Flue gases leaving a stack at 3000 C have an overall molar composition of 8.2% CO2 , 2.7% CO, 2.7% H2 0, 9.4% O2 and the rest N2 . Calculate the heat lost in 100 kg moles of this gas basing the gas on a datum temperature of 350 C. Assume water is in the vapor form. The constants for Cp are as follows: Gas a b x 103 c x 106 CO2 7.7 5.30 -0.83 CO 6.6 1.20 —H2 O (vapor) 8.2 0.15 1.34 O2 6.8 0.61 0.13 N2 6.8 0.61 0.13 Where Cp is in cal/g mol K and T is in K. [16] 8. (a) Define standard heat of reaction, heat of formation and heat of combustion (b) Calculate the heat of the following reaction, CaC2 + 2 H2 O → Ca(OH)2 + C2 H2 Heats of formation in cal/mol : CaC2 = -15000, H2 O = -68317 Ca(OH)2 = -235800, C2 H2 = 54194 ⋆⋆⋆⋆⋆ [8+8] 2 of 2 Code No: RR210803 Set No. 3 II B.Tech I Semester Supplementary Examinations, February 2007 MATERIAL & ENERGY BALANCE (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Write about the various hydrometers used in chemical industries to measure specific gravity of a solution. (b) Cracked gas from a petroleum refinery has the following composition by volume: methane 45%, ethane 10%, ethylene 25%, propane 7%, propylene 8%, n-butane 5%. Find the i. Average molecular weight of the gas mixture. ii. The composition by weight. iii. Specific gravity of the mixture. [6+5+5] 2. (a) Air is assumed to contain 79% nitrogen and 21% oxygen by volume. Calculate its density in grams per liter at a temperature of 210 C and a pressure of 741mm Hg. (b) It is desired to market oxygen in small cylinders having volumes of 0.01 cu m and each containing 0.4536 kg of oxygen. If the cylinders may be subjected to a maximum temperature of 490 C, calculate the pressure for which they must be designed, assuming the applicability of the ideal-gas law. [8+8] 3. (a) Calculate the total pressure and the composition of the vapors in contact with a solution at 1000 C containing 35% benzene (C6 H6 ), 40% toluene (C6 H5 CH3 ), and 25% orthoxylene (C6 H4 (CH3 )2 ) by weight. Vapor pressure at 1000C: Benzene = 1340 mm Hg, Toluene = 560 mm Hg, o-Xylene = 210 mm Hg. (b) State the Raoult’s law. What are the assumptions made in writing this law. [8+8] 4. (a) Write the principle of wet and dry thermometry. (b) A telescope gas holder contain 300 m3 of gas saturated with water vapor at 26. 50 C and a pressure of 11.2 mm Hg above atmosphere. The barometer reads 720 mm Hg. Calculate the weight of water vapour in the gas. Vapour pressure of H2 O at 26.50 C is 26.2 mm Hg. [8+8] 5. (a) Define: i. Overall fractional conversion. ii. Once through ( single pass ) conversion. (b) Write short notes on purging of inerts in recycle stock quoting industrial examples. [8+8] 1 of 2 Code No: RR210803 Set No. 3 6. A 1000-kg mixture of NaCl and NH4 Cl is to be separated by the fractional crystallization. It contains 40% NaCl by weight. It is dissolved in pure water at 323K. (a) If a stoichiometric quantity of water is used for dissolution calculate the quantity of the component remained undissolved and also the quantity of the saturated solution. (b) If the saturated solution at 323K mentioned above is cooled to 283K,calculate the additional quantity of the original mixture, which can be dissolved, and also the total quantity of the component remaining out of the solution. (c) If the saturated solution at 323K mentioned in (a) above is heated to 373K, calculate the additional quantity of the original mixture, which can be dissolved, and also the total quantity of the component remaining out of the solution. [5+5+6] Temperature K Solubility g/100g water NaCl NH4 Cl 283 18.25 12.49 323 14.26 22.50 373 10.77 33.98 7. Write short notes on: (a) Internal energy. (b) External energy. (c) Heat Work. 8. (a) Distinguish between heat of combustion and heat of reaction. (b) The standard heat of hydrogenation of gaseous propylene (C3 H6 ) to propane is –124 kJ. The heat of combustion of propane is –2.22 MJ at 25o C. Utilizing the known heats of formation of carbon dioxide (-393.6 kJ) and liquid water (-286 kJ), determine the heat of combustion and the standard heat of formation of propylene. [8+8] ⋆⋆⋆⋆⋆ [5+5+6] 2 of 2 Code No: RR210803 Set No. 4 II B.Tech I Semester Supplementary Examinations, February 2007 MATERIAL & ENERGY BALANCE (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. A liquid that is almost entirely water is reported to contain 125 ppb phenol (mass basis). (a) What is the mass fraction of phenol in the liquid? (b) How many milligrams of phenol are contained in one kilogram of the liquid? (c) What is the approximate concentration of phenol in the liquid in g/L? (d) What is the mole fraction of phenol in the liquid? [4×4] 2. (a) Calculate the volume occupied by 13.6 kg of chlorine at a pressure 743 mm Hg and 21.10C. (b) Calculate the weight of 3 cu.m of water vapor, measured at a pressure of 15.5 mm Hg and 230 C. [8+8] 3. (a) Write the Clausius-Clapeyron equation. State the assumptions made in its development. (b) Write a brief note on vapor pressure plots. (c) The vapor pressure of ethyl ether (molecular weight = 74) is 185 mm Hg at 00 C. The latent heat of vaporization is 92.5 cal/gm at 00 C. Calculate the vapor pressure at 20 and 350 C. [5+5+6] 4. It is desired to supply 3000 cu.m per min of air at 600 C, dew point 230 C to a soap drier. The outdoor air is available at 150 C, wet bulb 100 C. Indicate two ways of carrying out the change, stating temperatures and humidities involved. [16] 5. (a) A single effect evaporator concentrating a weak liquor containing 4% solids to 55% solids (by weight) is fed with 5000 kg of weak liquor per hour. Calculate i. Water evaporated per hour. ii. Flow rate of thick liquor. (b) A stream of oxygen is introduced into the NH3 pipe line at a rate of 4.5 m3 /min.The resulting mixture is sampled further down stream and found to contain 10% by volume of O2 . The entering oxygen is at 1.5 atm pressure and 303 K. Calculate the flow rates of NH3 and O2 in kg/hr. [8+8] 6. A saturated solution of KCl containing 1000kg solids at 900 C is cooled to 200 C, determine the yield of crystals. Solubility of KCl at 900 C: 53 parts /100 parts of water. Solubility of KCl at 200 C: 34.5 parts /100 parts of water. [16] 1 of 2 Code No: RR210803 Set No. 4 7. A gas mixture having 50 mole percent CO and 50 mole percent H2 is burnt in air, taken in 20% excess than the stoichiometric requirement. Both the gas mixture and air are taken at 25 0 C. Determine the temperature of the exhaust gases, assuming no heat losses and complete composition. Hc of CO = -57.1 kcal/mol ; Hc of H2 = - 57.8 kcal/mol Cp = a + b T + c T2 Cp in cal/gmol - k, T in K a b x 103 C x 106 N2 : 6.457 1.389 -0.069 -1.005 O2 : 6.117 3.167 CO2 : 6.339 10.140 -3.415 H2 0 : 7.136 2.640 0.046 [16] 8. When benzene (liquid) is completely burnt to CO2 (gas) and H2 O (liquid) the standard heat of combustion is -3263.5 × 103 kJ/kg mol. The standard heat of combustion of H2 (gas) to H2 O (liquid) is -285.8 × 103 kJ/kg mol, that of carbon (solid) to CO2 (gas) is -393.3 x 103 kJ/kg mol. Calculate the standard heat of formation of liquid benzene at constant volume neglecting the volume of water formed and initial volume of benzene. [16] ⋆⋆⋆⋆⋆ 2 of 2