• Author / Uploaded
• Carlo Luis Lee

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• Metanol
• Solución
• Cristalización
• Química Física
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CHECAL1 Problem Set # 3-1 Topic: Material Balances without Reaction.

AY 2009-2010 Engr. Lawrence Phoa Belo

1. (H) AARON Chemicals feeds a solution composed of 50% ethanol (EtOH), 10% methanol (MeOH), and 40% water (H2O) at the rate of 100 kg/hr into a separator that produces one stream at the rate of 60 kg/hr with the composition of 80% EtOH, 15% MeOH, and 5% H2O, and a second stream of unknown composition. a. Draw and label a process flowchart for AARON Chemicals and state the basis used. b. Calculate the composition (in %) of the three compounds in the unknown stream and its flowrate in kg/hr. 2. (H) 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. 3. (H) Mike is asked to measure the rate at which waste gases are being discharged from a stack. The gases entering contain 2.1 % carbon dioxide. Pure carbon dioxide is introduced into the bottom of the stack at a measured rate of 4.0 lb per minute. He measures the discharge of gases leaving the stack, and finds the concentration of carbon dioxide to be 3.2 %. What would the rate of flow, in lb mol/minute, be of the entering waste gases? 4. (H) A crystallizer contains 6420 lb of aqueous solution of anhydrous sodium sulphate (concentration 29.6 wt %) at 104 °C. The solution is cooled to 20 °C to crystallize out the desired Na2SO4  10 H2O. The remaining solution (the mother liquor) is found to contain 16.1 % anhydrous sodium sulfate. What is the weight of this mother liquor? What is the composition of the mother liquor? 5. (R4.3) A liquid mixture of benzene and toluene contains 55.0% benzene by mass. The mixture is partially evaporated to yield a vapour containing 85% benzene and a residual liquid containing 10.6% benzene by mass. Suppose the process is to be carried out continuously and at a steady state, with a feed rate of 100.0 kg/h of the 55.0% mixture. Let mv (kg/h) & ml (kg/h) be the mass flowrates of the vapour & liquid product streams, respectively. a. Draw and label a process flowchart b. Indicate the basis chosen and solve for the unknowns. 6. (R4.8) Eggs are sorted into two sizes (Large and Extra large) at the CHECAL’s Cheerful Chicken House. Unfortunately business has not been good lately, and since the CHECAL’s Cheerful Chicken’s 40-year-old egg-sorting machine finally gave up, there have been no funds to replace it. Instead, Pedro, one of the firm’s sharper-eyed employees, have been equipped with a “Large” rubber stamp in his right hand and an “X-large” rubber stamp in his left hand and assigned to stamp each egg with the appropriate label as it goes by on the conveyor belt. Down the line, another employee, Juan, puts the eggs into either of the two hoppers, each egg according to its stamp. The system works reasonably well, all things considered, except Juan notices that Pedro has a heavy hand and on the average breaks 30% of the 120 eggs that pass by him each minute. At the same time, a check on the “X-large” stream reveals a flow rate of 70 eggs/min, of which 25 eggs/min are broken. a. Draw and label a process block diagram/flowchart b. Write and solve balances about the egg sorter on total eggs and broken eggs c. How many “large” eggs leave the plant each minute, and what fraction is broken? d. Is Pedro right or left-handed? Justify. 7. (R4.9) Strawberries contain about 15% wt solids and 85% wt water. To make strawberry jam, ENZO’s Sweet Shop mixes crushed strawberries and sugar in a 45:55 mass ratio, and the mixture is heated to evaporate water until the residue contains one-third water by mass. a. Draw and label a flowchart for the process b. Calculate how many pounds of strawberries are needed to make a pound of jam? c. How much water was evaporated?

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