!Checal Reviewer

November 18, 2018 | Author: cctolentino1 | Category: Carbon Dioxide, Titanium Dioxide, Combustion, Methane, Silicon Dioxide
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CHEMICAL ENGINEERING CALCULATIONS

1) Gypsum (plaster of Paris : CaSO 4. 2H2O) is produced by the reaction of calcium carbonate and sulfuric acid. A certain lime stone analyzes: CaCO 3 96.89 %; MgCO3 1.41 %; inerts 1.70 %. For 5 metric tons of  limestone reacted completely, determine: a. kg of anhydrous gypsum (CaSO 4) produced. produced. b. kg of sulfuric sulfuric acid solution (98 wt%) required. c. kg of carbon dioxide produced. (MW: CaCO3 100.1; MgCO3 84.32; H2SO4 98; CaSO4 136; MgSO4 120; H2O 18; CO2 44) a. 6577 b. 4836 c. 2128 2) The synthesis of ammonia proceeds according to the following reaction N2 + 3 H2 → 2 NH3 In a given plant, 4202 lb of nitrogen and 1046 lb of hydrogen are fed to the synthesis reactor per hour. Production of pure ammonia from this reactor is 3060 lb per hour. a.) What is is the limiting reactant reactant b.)What is the percent excess excess reactant. c. What is the percent conversion obtained (based on the limiting reactant). a. N2 b. 15.31 % excess H2 c. 59.89% 3) Five pounds of bismuth (MW = 209) is heated along with one pound of sulfur to form Bi2S3 (MW = 514). At the end of t he reaction, the mass is extracted and the free sulfur recovered is 5% of the reaction mass. Determine a.) the limiting reactant. b.) the percent excess reactant. c.) the percent conversion conversion of sulfur to to Bi2S3. 2 Bi + 3 S → Bi 2S3 a. S b. 14.83% c. 70% 4) A liquid adhesive, which is used to make laminated boards, consists of a polymer dissolved in a solvent. The amount of polymer in the solution has to be carefully controlled for this application. When the supplier of the adhesive receives an order for 3000 kg of an adhesive solution containing 13 wt % polymer, all it has on hand is (1) 500 kg of a 10 wt % solution, (2) a very large quantity of a 20 wt % solution, and (3) pure solvent. Calculate the weight of each of the three stocks that must be blended together to fill the order. Use all of the 10 wt % solution. All of (1), 2040 kg of (2), and 460 kg of (3) 5) A cement clinker with the following analysis: CaO = 64% SiO2 = 21%

Fe2O3 = 6.5% Al2O3 = 7.5%

Is produced at a rate of 2000 MT per day. The materials used are limestone (CaCO 3 and inert materials) containing 97% CaO; iron oxide (Fe 2O3 and inert materials) containing 85% Fe2O3; Shale (SiO2, Al 2O3 and inerts) containing 60% SiO2 and 25% Al2O3 and silica with 90% SiO 2 and 10% inerts. The MT of silica required for a 300 -day operation per year is a. 20,000 b. 30,000 c. 25,000 d. 35,000 6) Solid Calcium fluoride (CaF 2) reacts with sulfuric acid to form solid calcium sulfate and gaseous hydrogen fluoride. The HF is then dissolved in water to form hydrofluoric acid. A source of calcium fluoride is fluorite ore containing 96.0 wt% CaF 2 and 4% SiO2.

By: JACY   July 2010  Code: CHECAL-001

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CHEMICAL ENGINEERING CALCULATIONS

In a typical hydrofluoric acid manufacturing process, fluorite ore is reacted with 93 wt% aqueous sulfuric acid, supplied 15% excess of the stoichiometric amount. Ninety-five percent of the ore dissolves in the acid. Some of the HF for med reacts with the dissolved silica in the reaction 6 HF + SiO2 (aq) → H2SiF6(s) + 2 H2O (l) The hydrogen fluoride exiting from the reactor is subsequently dissolved in enough water to produce 60.0wt% hydrofluoric acid. Calculate the quantity of fluorite ore needed to produce a metric ton of acid. Note: Some of the given data are not needed to solve t he problem. 1232 kg 7) TiCl4 can be formed by reacting titanium dioxide (TiO 2) with hydrochloric acid. TiO 2 is available as an ore containing 78 % TiO 2 and 22 % inerts. The HCl is available as 45 wt% solution (the balance is water). The per pass conversion of TiO 2 is 75 %. The HCl is fed into the reactor in 20 % excess based on the reaction. Pure unreacted TiO2 is recycled back to mix with the TiO 2 feed. TiO2 + 4 HCl -----> TiCl4 + 2 H2O For 1 kg of TiCl4 produced, determine: a.) the kg of TiO2 ore fed. b.) the kg of 45 wt % HCl solution fed. c.) the ratio of recycle stream to fresh TiO2 ore (in kg). (MW : TiO 2 79.9; HCl 36.47; TiCl4 189.7) 8) The reactions C2H6 → C2H4 + H2 C2H6 + H2 → 2CH4 Take place in a continuous reactor at steady state. The feed contains 85.0 mole% ethane (C 2H6) and the balance inerts (I). The fractional conversion of ethane is 0.501, and the fractional yield of ethylene is 0.471. Calculate the molar composition of the product gas and the selectivity of ethylene to methane production. 28.59% C2H4, 30.29% C2H6, 10.71% inerts, 26.77% H2, 3.64% CH4; Selectivity: 7.85 9) Methane and oxygen react in the presence of a catalyst to form formaldehyde. In a parallel reaction methane is oxidized to carbon dioxide and water: CH4 + O2 → HCHO + H 2O CH4 + 2O2 → CO2 + 2H2O The feed to the reactor contains equimolar amounts of methane and oxygen. Assume a basis of 100 mol feed/s. The fractional conversion of methane is 0.900 and the fractional yield of formaldehyde is 0.855. Calculate the molar composition of the reactor output stream and the selectivity of formaldehyde production relative to carbon dioxide production. Output: 9.48% CH4, 5.21% O2, 81 .04% HCHO, 4.27% CO2; selectivity = 19 10) Ethane is chlorinated in a continuous reactor: C2H6 + Cl2 → C2H5Cl + HCl Some of the product monochloroethane is further chlorinated in an undesired side reaction: C2H5Cl + Cl2 → C2H4Cl2 + HCl The reactor is designed to yield a 15% conversion of ethane and a selectivity of 14mol C2H5Cl/mol C2H4Cl2, with a negligible amount of chlorine in the product gas. Calculate the feed ratio (mol Cl 2/mol C2H6) and the fractional yield of monochloroethane. Feed ratio: 0.1875; fractional yield = 11.25%

By: JACY   July 2010  Code: CHECAL-001

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CHEMICAL ENGINEERING CALCULATIONS

11) What will be the percent carbon monoxide in flue gas from the burning of carbon with 50% excess air in such a manner that 80% carbon burns to carbon dioxide and the rest to carbon monoxide? Ans.

2.76% 12) A pure saturated hydrocarbon is burnt with excess air. The Orsat analysis of the stack gas shows 7.9%CO2, 1.18%CO, 0.24%H2, 5.25%O2, and 85.43%N2. Calculate the percent excess air and the formula of the hydrocarbon. Ans. 24.99% CH4 13) A mixture containing 9 mole% methane in air flowing at a rate of 700 kg/h is to be diluted with pure air to reduce the methane concentration to the lower flammability limit (5% methane). Calculate the required flow rate of air in mol/hr. Take MW of Air = 29.

20,119.39 14) Acetylene is hydrogenated to form ethane. The feed to the reactor contains 1.5mol H 2/mol C2H2. 6 Calculate the mass feed of hydrogen (kg/s) required to produce 4 x 10 metric tons of ethane per year, assuming the reaction goes to completion and that the process operates 24 hrs a day and 300 days Ans. 20.69 15) A gas containing equimolal oxygen and nitrogen is passed through a membrane to separate the oxygen from the nitrogen. The final product is found to contain 40% O2 and 60% N2. Find the percentage of O2 in the remaining gas if only 35% of the original feed passed through the membrane. Ans. 55.38% 16) A fuel oil is analyzed and found to contain 85 wt% carbon, 12% elemental hydrogen, 1.7% sulfur, and the remainder noncombustible matter. The oil is burned with 20% excess air. The oil is burned completely, but 8% of the carbon forms CO. Calculate in mole percent the CO and CO 2 composition of  the stack gas. Ans. 10.71% CO2 and 0.93% CO 17) A vacuum crystallizer is fed with 2000 kg/hr of a 25% Na 2SO4 solution. If the products leave the o crystallizer at 60 F, and 4% of the water in the feed is evaporated, what is the production rate of  o Glauber's salt (Na2SO4.10H20)? Solubility at 60 F is 12% Na2SO4. Molecular weight of Na 2SO4 = 142 Ans. 832.42 kg/hr 18) Consider a continuous steady-state process in which the following reactions take place: C6H12 + 6 H2O → 6 CO + 12 H2 C6H12 + H2 → C6H14 In process 250 moles ofC 6H12 and 800 moles of H2O are fed into the reactor each hour. The yield of H 2 is 40.0% and the selectivity of H 2 relative to C6H14 is 12.0. Calculate the molar flow rates of all five components in the output stream. 21.24% CO, 27.77% H2O, 39.21% H2, 3.27% C6H14, 8.51% C6H12 [mol/hr] 19) In the anaerobic fermentation of grain, the yeast Saccharomyces cerevisiae digests glucose from plants to form the products ethanol and propenoic acid by following the overall reactions: Reaction 1: C6H12O6 → 2 C2H5OH + 2 CO2 Reaction 2: C6H12O6 → 2 C2H3CO2H + 2 H2O In a batch process, a tank is charged with 4000 kg of a 12% glucose/water solution. After fermentation 120 kg of carbon dioxide are produced together with 90 kg of unreacted glucose. What are the weight

By: JACY   July 2010  Code: CHECAL-001

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CHEMICAL ENGINEERING CALCULATIONS

percents of ethyl alcohol and propenoic acid remaining in the broth? Assume that none of the glucose is assimilated into the bacteria.

3.14% ethanol, 2.89% propenoic acid 20) The analysis of a sample of Babul bark (of northern India) yield 5.8% moisture, 12.6% tannin, 8.3% soluble non-tannin organic matter and the rest lignin. In order to extract tannin out of the bark, a counter-current extraction process is employed. The residue from the extraction process is analyzed and found to contain 0.92% tannin and 0.65% solute non-tannin organic matter on a dry basis. Find the percentage of tannin recovered on the basis of the original tannin present in the bark. All analysis are given on mass basis.

By: JACY   July 2010  Code: CHECAL-001

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