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Separation Processes in Chemical Engineering, Exams of Chemical Separation Processes

Benguet State University (BSU)Chemical Separation Processes

Various separation processes and principles in chemical engineering, including distillation, extraction, adsorption, and thermodynamic concepts. It provides detailed information on topics such as relative volatility, equilibrium curves, feed quality, operating lines, and mccabe-thiele method. The document also discusses equations of state, heat transfer, mass transfer, and absorption processes. It covers a wide range of chemical engineering principles and their applications, making it a valuable resource for students and professionals in the field.

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CHEMICAL ENGINEERING CALCULATIONS
CHEMICAL ENGINEERING PRINCIPLES
Chemical Engineering Calculations 1
For numbers 1 to 3:
Wine making involves a series of very complex reactions most of
which are performed by microorganisms. The starting
concentration of sugars determines the final alcohol content and
sweetness of the wine. The specific gravity of the starting stock
is therefore adjusted to achieve desired quality of wine. A starting
stock solution has a specific gravity of 1.075 and contains 12.7
wt% sugar. If all the sugar is assumed to be C12H22O11, determine
1. kg sugar / kg H2O
a. 0.286 c. 0.145
b. 0.039 d. 0.327
2. lb solution / ft3 solution
a. 67.1 c. 50.5
b. 39.2 d. 48.6
3. g sugar / L solution
a. 202 c. 295
b. 136 d. 144
For numbers 4 to 6:
Two aqueous sulfuric acid solutions containing 20 wt% H2SO4
(SG=1.139) and 60 wt% H2SO4 (SG=1.498) are mixed to form a
4 M solution (SG=1.213).
4. Calculate the mass fraction of sulfuric acid in the product solution.
a. 0.105 c. 0.323
b. 0.667 d. 0.548
5. Calculate the feed ratio (liters 20% solution per liter 60% solution)
a. 2.96 c. 1.75
b. 3.08 d. 4.51
6. What feed rate of the 60% solution (L/hr) would be required to
produce 1250 kg/h of the product.
a. 986 L/h c. 110 L/h
b. 257 L/h d. 462 L/h
For numbers 7 to 8:
If 1 L of ethyl alcohol is mixed with 1 L of water at 200C.
7. How many kilograms of solution result?
a. 1.85 kg c. 1.79 kg
b. 2.06 kg d. 2.11 kg
8. How many liters?
a. 1.93 L c. 2.00 L
b. 1.88 L d. 2.15 L
9. Air is bubbled through a drum of liquid hexane at a rate of 0.10
kmol/min. The gas stream leaving the drum contains 10 mol%
hexane vapor. Air may be considered insoluble in liquid hexane.
Use an integral balance to estimate the time required to vaporize
10 m3 of the liquid.
a. 4200 min c. 7700 min
b. 6900 min d. 8100 min
10. Urea, phosphoric acid and potassium chloride are mixed together
to obtain a mixed fertilizer having NPK content 10:26:26 as %N,
%P2O5 and %K2O by weight, balance being the weight of filler
materials. Calculate the amount of potassium chloride to be
mixed to get 1000 kg of mixed fertilizer.
a. 214.4 kg c. 411.5 kg
b. 359 kg d. 505 kg
11. A supplier shipped a material for chicken feed with the following
analytical report: protein – 22%, triglyceride – 8%, moisture –
10%. During transport moisture was picked up by the material;
the later analytical report showed 14% moisture. Based on the
latest report, recalculate the % triglyceride.
a. 21.02% c. 7.64%
b. 39.33% d. 14.65%
For numbers 12 to 14:
An evaporator is fed continuously with 25 MT/h of a solution
consisting of 10% NaOH, 10% NaCl, and 80% H2O. During
evaporation, water is boiled off, and salt precipitates as crystals,
which are settled and removed from the remaining liquor. The
concentrated liquor leaving the evaporator contains 50% NaOH,
2% NaCl and 48% H2O.
12. Calculate the kg of water evaporated per hour
a. 19300 c. 17600
b. 18500 d. 16200
13. Calculate the kg salt precipitated per hour
a. 2400 c. 1100
b. 3500 d. 4700
14. Calculate the kg of concentrated liquor produced per hour
a. 4000 c. 6000
b. 3000 d. 5000
For numbers 15 to 16:
Ten kilograms each of salts A and B are dissolved in 50 kg of
water. The solubility of A in water is 1 kg per kg water and that of
B is 0.5 kg per kg of water. The solution is heated to evaporate
water. When the concentration of the solution reaches the
saturation concentration of any salt, further evaporation results in
the crystallization of that salt. If 70% of the water that is originally
present in the solution is driven off by evaporation, determine the
following:
15. The weight of the final solution
a. 46.5 c. 11.5
b. 28.5 d. 32.5
16. The weight of the crystals formed
a. 2.5 c. 0
b. 5.5 d.1.5
17. 1200 lb of barium nitrate is dissolved in sufficient water to form a
saturated solution at 900C. Assuming that 5% of the weight of the
original solution is lost through evaporation calculate the crop of
crystals obtained when cooled at 200C. Solubility data for barium
nitrate at 900C is 30.6% wt and 8.6 wt% at 200C.
a. 952.4 lbs c. 962.4 lbs
b. 970 lbs d. 980 lbs
18. What is the theoretical yield of crystals which may be obtained by
cooling a solution containing 1000 kg of sodium sulfate (mw = 142
kg/kmol) in 5000 kg water to 283 K? The solubility of sodium
sulfate at 283 K is 9 kg anhydrous salt / 100 kg water and the
deposited crystals will consist of decahydrate. It may be assumed
that 2% of the water will be lost by evaporation during cooling.
a. 4469.17 kg c. 6000 kg
b. 250 kg d. 1430.83 kg
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CHEMICAL ENGINEERING CALCULATIONS

CHEMICAL ENGINEERING PRINCIPLES

Chemical Engineering Calculations 1

For numbers 1 to 3: Wine making involves a series of very complex reactions most of which are performed by microorganisms. The starting concentration of sugars determines the final alcohol content and sweetness of the wine. The specific gravity of the starting stock is therefore adjusted to achieve desired quality of wine. A starting stock solution has a specific gravity of 1.075 and contains 12. wt% sugar. If all the sugar is assumed to be C 12 H 22 O 11 , determine

  1. kg sugar / kg H 2 O a. 0.286 c. 0. b. 0.039 d. 0.
  2. lb solution / ft^3 solution a. 67.1 c. 50. b. 39.2 d. 48.
  3. g sugar / L solution a. 202 c. 295 b. 136 d. 144 For numbers 4 to 6 : Two aqueous sulfuric acid solutions containing 20 wt% H 2 SO 4 (SG=1.139) and 60 wt% H 2 SO 4 (SG=1.498) are mixed to form a 4 M solution (SG=1.213).
  4. Calculate the mass fraction of sulfuric acid in the product solution. a. 0.105 c. 0. b. 0.667 d. 0.
  5. Calculate the feed ratio (liters 20% solution per liter 60% solution) a. 2.96 c. 1. b. 3.08 d. 4.
  6. What feed rate of the 60% solution (L/hr) would be required to produce 1250 kg/h of the product. a. 986 L/h c. 110 L/h b. 257 L/h d. 462 L/h For numbers 7 to 8 : If 1 L of ethyl alcohol is mixed with 1 L of water at 20^0 C.
  7. How many kilograms of solution result? a. 1.85 kg c. 1.79 kg b. 2.06 kg d. 2.11 kg
  8. How many liters? a. 1.9 3 L c. 2.0 0 L b. 1.8 8 L d. 2.1 5 L
  9. Air is bubbled through a drum of liquid hexane at a rate of 0. kmol/min. The gas stream leaving the drum contains 10 mol% hexane vapor. Air may be considered insoluble in liquid hexane. Use an integral balance to estimate the time required to vaporize 10 m^3 of the liquid. a. 4200 min c. 7700 min b. 6900 min d. 8100 min
  10. Urea, phosphoric acid and potassium chloride are mixed together to obtain a mixed fertilizer having NPK content 10:26:26 as %N, %P 2 O 5 and %K 2 O by weight, balance being the weight of filler materials. Calculate the amount of potassium chloride to be mixed to get 1000 kg of mixed fertilizer. a. 214.4 kg c. 411.5 kg b. 359 kg d. 505 kg
    1. A supplier shipped a material for chicken feed with the following analytical report: protein – 22%, triglyceride – 8%, moisture – 10%. During transport moisture was picked up by the material; the later analytical report showed 14% moisture. Based on the latest report, recalculate the % triglyceride. a. 21.02% c. 7.64% b. 39.33% d. 14.65% For numbers 12 to 14: An evaporator is fed continuously with 25 MT/h of a solution consisting of 10% NaOH, 10% NaCl, and 80% H 2 O. During evaporation, water is boiled off, and salt precipitates as crystals, which are settled and removed from the remaining liquor. The concentrated liquor leaving the evaporator contains 50% NaOH, 2% NaCl and 48% H 2 O.
    2. Calculate the kg of water evaporated per hour a. 19300 c. 17600 b. 18500 d. 16200
    3. Calculate the kg salt precipitated per hour a. 2400 c. 1100 b. 3500 d. 4700
    4. Calculate the kg of concentrated liquor produced per hour a. 4000 c. 6000 b. 3000 d. 5000 For numbers 15 to 16 : Ten kilograms each of salts A and B are dissolved in 50 kg of water. The solubility of A in water is 1 kg per kg water and that of B is 0.5 kg per kg of water. The solution is heated to evaporate water. When the concentration of the solution reaches the saturation concentration of any salt, further evaporation results in the crystallization of that salt. If 70% of the water that is originally present in the solution is driven off by evaporation, determine the following:
    5. The weight of the final solution a. 46.5 c. 11. b. 28.5 d. 32.
    6. The weight of the crystals formed a. 2.5 c. 0 b. 5.5 d.1.
    7. 1200 lb of barium nitrate is dissolved in sufficient water to form a saturated solution at 90^0 C. Assuming that 5% of the weight of the original solution is lost through evaporation calculate the crop of crystals obtained when cooled at 20^0 C. Solubility data for barium nitrate at 90^0 C is 30.6% wt and 8.6 wt% at 20^0 C. a. 952.4 lbs c. 962.4 lbs b. 970 lbs d. 980 lbs
    8. What is the theoretical yield of crystals which may be obtained by cooling a solution containing 1000 kg of sodium sulfate (mw = 142 kg/kmol) in 5000 kg water to 283 K? The solubility of sodium sulfate at 283 K is 9 kg anhydrous salt / 100 kg water and the deposited crystals will consist of decahydrate. It may be assumed that 2% of the water will be lost by evaporation during cooling. a. 4469.17 kg c. 6000 kg b. 250 kg d. 1430.83 kg

CHEMICAL ENGINEERING CALCULATIONS

CHEMICAL ENGINEERING PRINCIPLES

  1. A solution of NH 4 Cl is saturated at 700 C. Calculate the temperature to which this solution must be cooled in order to crystallize out of 45% of the NH 4 Cl. The solubility of NH 4 Cl in water are: Temperature, 0 C Solubility, g/100g H 2 O 70 60. 10 33. 0 29. a. 8.6 c. 9. b. 5.7 d. 7.
  2. In the azeotropic distillation of an ethanol–water solution, a feed mixture containing 95.6% alcohol is mixed with pure benzene and distilled. The benzene forms a ternary azeotrope with alcohol– water with a composition of 74.1% benzene, 7.4% water and 18.5% alcohol, which is distilled over as the overhead product. Absolute alcohol is obtained as the residue product. Determine the quantity of benzene required for producing 100 kg of absolute alcohol. a. 48 kg c. 66 kg b. 74 kg d. 52 kg
  3. Oil is extracted from seeds by leaching with organic solvents. Soybean seeds containing 20% oil, 65% inert solids and 15% water are leached with hexane and after extraction the solid residue is removed from the solution of oil in hexane. The residue analyzed 1.0% oil, 88% inert cake and 11% water. What percent of oil is recovered? a. 90% c. 96% b. 82% d. 87%
  4. Acetone is recovered from an acetone-air mixture containing 25% (volume) acetone by scrubbing with water. Assuming that air is insoluble in water, determine the percent of acetone in the entering gas that is absorbed if the gas leaving the scrubber analyzes 5% acetone. a. 96% c. 65% b. 84% d. 73%
  5. One hundred pounds of solution containing 80 wt% Na 2 SO 4 must be obtained by evaporating a dilute solution using a double effect evaporator. If the evaporator from the 2nd effect is 60% of that coming from the first effect and the concentrate of the first effect contains 1 lb Na 2 SO 4 per pound of water. Calculate for the composition of the feed. a. 69% Na 2 SO 4 c. 4 5% Na 2 SO 4 b. 55% Na 2 SO 4 d. 31% Na 2 SO 4
  6. One drier will dry a material from 45% moisture (wb) to 20% moisture (db) from here the material enters another drier where the H 2 O content is further reduced to give a final product weighing 1000 kg. If the total evaporation from both driers is 800 kg, the moisture of the final product is a. 5% c. 2% b. 3% d. 1% For numbers 25 to 26 : An aqueous solution containing 15% NaOH and 0.5% NaCl is concentrated at a rate of 100 kg/min in an evaporator. The concentrated solution is then mixed with 2000 kg of aqueous NaOH solution in a mixer. At the end of one hour a sample is collected from the mixer and analyzed. The analysis shows 40% NaOH and 0.8574% NaCl. Calculate the following:
    1. The concentration of the original solution in the receiver a. 32% NaOH c. 40% NaOH b. 25% NaOH d. 56% NaOH
    2. The mass of water (in kilograms) evaporated in one hour a. 3 200 kg c. 4 500 kg b. 5100 kg d. 6600 kg For numbers 27 to 29 : For the preparation of potassium nitrate, 10000 kg/h of a 20% KNO 3 solution is mixed with a recycle stream and sent to an evaporator. The rate of evaporation is 1.5 times the rate of introduction of recycle stream. The concentrated solution leaving the evaporator contains 50% KNO 3. This is admitted to the crystallizer which yields crystals containing 5% water. At the crystallization temperature the solubility is 50 kg/100 kg of water. The major part of the mother liquor leaving the crystallizer is returned to the crystallizer as recycle. Calculate the following:
    3. The concentration of KNO 3 in the stream entering the evaporator a. 33% c. 16% b. 25% d. 40%
    4. The flow rate of recycle stream in kg/h a. 5143 c. 1354 b. 45 31 d. 34 15
    5. The rate of production of crystals a. 3925 c. 1588 b. 2007 d. 4610 For numbers 30 to 32 : Fresh air containing 4 mol% water vapor is to be cooled and dehumidified to a water content of 1.70 mol% H 2 O. A stream of fresh air is combined with a recycle stream of previously dehumidified air and passed through the cooler. The blended stream entering the unit contains 2.3 mol% H 2 O. In the air conditioner, some of the water in the feed stream is condensed and removed as liquid. A fraction of the dehumidified air leaving the cooler is recycled and the remainder is delivered to a room. Taking 100 mol of dehumidified air delivered to the room as a basis of calculation, calculate the following:
    6. The moles of fresh feed a. 115 mol c. 102 mol b. 126 mol d. 133 mol
    7. The moles of water condensed a. 0.8 mol c. 2.4 mol b. 1.0 mol d. 3.3 mol
    8. The moles of dehumidified air recycled a. 270 mol c. 280 mol b. 290 mol d. 260 mol For numbers 33 to 35 : An equimolar liquid mixture of benzene and toluene is separated into two product streams by distillation. A process flowchart and a somewhat oversimplified description of what happens in the process follow:

CHEMICAL ENGINEERING CALCULATIONS

CHEMICAL ENGINEERING PRINCIPLES

  1. In the Deacon process for the manufacture of chlorine, HCl and O 2 react to form Cl 2 and H 2 O. Sufficient air is fed to provide 35% excess oxygen and the fractional conversion of HCl is 85%. Calculate the mole fraction of water in the product stream. a. 0.18 c. 0. b. 0.12 d. 0.
  2. Phenol (94) can be manufactured by reacting chlorobenzene (112.45) with sodium hydroxide (40). To produce 1000 kg of phenol, 1200 kg of sodium hydroxide and 1,320 kg of chlorobenzene are used. What is the maximum conversion of the excess reactant? a. 29.66% c. 31.05% b. 35.47% d. 39.13% For numbers 49 to 50 : Acrylonitrile is produced in the reaction of propylene, ammonia and oxygen: C 3 H 6 + NH 3 + 3/2 O 2 à C 3 H 3 N + 3 H 2 O The feed contains 10 mole % propylene, 12 mole% ammonia, and 78% air. A fractional conversion of 30% of the limiting reactant is achieved. Taking 100 mol of feed as basis, determine the following:
  3. The percentage by which of the reactants in excess a. 24%, 6.2% c. 25%, 8.5% b. 28%, 7.5% d. 20%, 9.2%
  4. The mole% of water in the product gas a. 6% c. 5% b. 7% d. 9% For numbers 51 to 53 : Given the reaction of ethyl tetrabromide with zinc dust produces C 2 H 2 and ZnBr 2. Based on the C 2 H 2 Br 4 , on one pass through the reactor the conversion is 80%, and the unreacted C 2 H 2 Br 4 is recycled. On the basis of 1000 kg/hr of C 2 H 2 Br 4 fed to the reactor per hour, calculate
  5. The rate of recycle in lb/hr a. 150 kg c. 350 kg b. 250 kg d. 450 kg
  6. The amount of Zn that has to be added per hour if Zn is to be 20% in excess a. 233 kg c. 454 kg b. 116 kg d. 378 kg
  7. The mole ratio of ZnBr2 to C 2 H 2 in the products a. 1.5 c. 2. b. 1.0 d. 2. For numbers 54 to 56 : TiCl 4 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 TiO2is recycled back to mix with the TiO 2 feed. TiO 2 + 4 HCl à TiCl 4 + 2H 2 O For 1 kg of TiCl 4 produced, determine:
    1. The kg of TiO 2 ore fed. a. 0.26 c. 2. b. 0.54 d. 1.
    2. The kg of 45 wt % HCl solution fed. a. 0.26 c. 2. b. 0.54 d. 1.
    3. The ratio of recycle stream to fresh TiO 2 ore (in kg). a. 0.26 c. 2. b. 0.54 d. 1. For numbers 57 to 58 : Propane is dehydrogenated to form propylene in a catalytic reactor. The process is to be designed for a 95% overall conversion of propane. The reaction products are separated into two streams: the first, which contains H 2 , C 3 H 6 , and 0.555% of the propane that leaves the reactor, is taken off as a product; the second stream, which contains the balance of the unreacted propane and 5% of the propylene in the first stream, is recycled to the reactor.
    4. Calculate the ratio of moles recycled / mole fresh feed a. 1.2 c. 2. b. 6.8 D. 9.
    5. What is the single-pass conversion? a. 9.6% c. 25.0% b. 13.5% d. 38.2%

Chemical Engineering Calculations II

For numbers 59 to 61 : Butane is burned with air. No carbon monoxide is present in the combustion products. Calculate the molar composition of water in the product gas for each of the following cases:

  1. Theoretical air supplied, 100% conversion of butane a. 12.0% c. 3.3% b. 14.9% d. 10.7%
  2. 20% excess air, 100% conversion of butane a. 12.6% c. 15.2% b. 8.8% d. 10.1%
  3. 20% excess air, 90% conversion of butane a. 9.1% c. 11.4% b. 13.6% d. 7.5% For numbers 62 to 63: A fuel containing 75% ethane and 25% propane is burned with dry air. All the H 2 burns to H 2 O and the CO 2 to CO ratio is 10:1. Fifteen% excess air is supplied. Calculate:
  4. Percent CO in the Orsat analysis of stack gas a. 1.04% c. 5.33% b. 2.18% d. 4.27%
  5. Percent CO in the complete analysis of stack gas a. 0.65% c. 0.89% b. 0.33% d. 0.99%

CHEMICAL ENGINEERING CALCULATIONS

CHEMICAL ENGINEERING PRINCIPLES

For number 64 to 65 : Orsat analysis of the stack gas from the combustion of a gaseous mixture of acetylene and methane shows 9.82% CO 2 , 1.37%CO, 0.69% H 2 , 5.43% O 2 and 82.69% N 2. Determine:

  1. The % excess air a. 15% c 10% b. 20% d. 25%
  2. The % mol CH 4 in the gaseous fuel a. 50% c. 40% b. 30% d. 60% For numbers 66 to 67 : A pure saturated hydrocarbon is burnt with excess air. Orsat analysis of the stack gas shows 7.9% CO 2 , 1.18% CO, 0.24% H 2 , 5.25% O 2 , and 85.43% N 2. Air is substantially dry. The stack gases leave at 750 mmHg pressure. Calculate:
  3. The % excess air a. 25% c 18% b. 34% d. 44%
  4. The formula of the hydrocarbon a. CH 4 c C 3 H 8 b. C 2 H 6 d. C 4 H 10
  5. The burning of pure butane with excess air gives a stack gas which analyzes 11.55% CO 2 on a dry basis. Assuming complete combustion, calculate the % excess air a. 16% c. 11% b. 20% d. 23%
  6. The octane number of a gasoline was determined using a mixture of isooctane and n-heptane with the same knocking tendency as the gasoline If the iso-octane - heptane mixture is burned in 30% excess air, with a product gas molal ratio of CO 2 to CO of 5:2 and H 2 to CO of 1:1, what is the % CO in the Orsat analysis? Assume octane number of 85. Density of iso-octane is 0.6918 and n- heptane is 0.684 g/ml. a. 3.03% c. 2.95% b. 1.56% d. 4.47%
  7. If the test study on the combustion of the cetane-methyl naphthalene mixture gave a product gas analyzing 7.14% CO 2 , 4.28% CO, 8.24% O 2 and 80.34% N 2 , what is the cetane number of the diesel. Density of cetane is 0.7751 and methyl naphthalene is 1.025 g/ml. a. 28 c. 53 b. 36 d. 45 For numbers 71 to 75 : A furnace is fired with sub bituminous B coal containing 10.3% moisture, 34% VCM and 7.7% ash. It is also known to contain 1.2% N and 1.57% S. Its calorific value is 22 MJ/kg. Calculate its:
  8. % Fixed carbon a. 55% c. 48% b. 37% d. 62%
  9. % Combined water a. 22.5% c. 18.5% b. 10.7% d. 35.9%
  10. % Oxygen a. 29% c. 38% b. 40% d. 15%
    1. % Combined water in VCM a. 55% c. 66% b. 44% d. 33%
    2. Calorific Value of VCM. a. 12 MJ/kg c. 15 MJ/kg b. 17 MJ/kg d. 10 MJ/kg For numbers 76 to 77 : A furnace is fired with high volatile A bituminous coal whose ultimate analysis shows 75.2% C, 5.19% H, 8.72% O, 1.5% N, 7.8% ash and 1.6% S. 60% excess air is supplied. Assume CO to CO 2 ratio of 0.175. The stack gas leaves at 300^0 C, 740 torrs. Calculate:
    3. The % water in the complete analysis of the stack gas if air is supplied at 28^0 C, 100 kPa and essentially dry. a. 2.06% c. 3.12% b. 5.90% d. 4.47%
    4. The calorific value of the coal. a. 28 MJ/kg c. 31 MJ/kg b. 25 MJ/kg d. 39 MJ/kg For numbers 78 to 79: A high volatile B bituminous coal analyzing 22% VCM, 64% FC, 4% M, 1.4% N and 1.6% S has a calorific value of 32.5 MJ/kg. It is burned in excess air supplied essentially dry at 2 80 C and 1 atm. The stack gases leave at 25^0 C, 740 mmHg and contain 8.37% CO 2 , 4.19% CO and 2.51% H 2. Calculate:
    5. The % excess O 2 a. 38% c. 55% b. 40% d. 62%
    6. The % N 2 in the complete Orsat analysis of the stack gas a. 75% c. 76% b. 89% d. 80%
    7. A furnace burns coal with the following analysis: M – 4.1%, VCM
     - 24%, FC – 63.0%, N – 1.20%, S – 1.80%, Ash – 8.90%. The refuse analyzed 4.8% VCM, 12.6% FC, 82.6% ash and a calorific value of 32 MJ/kg. Calculate the percentage of gross calorific value lost in the refuse. a. 1.38% c. 0.90% b. 2 .16% d. 3.05%

SEPARATION PROCESSES

CHEMICAL ENGINEERING PRINCIPLES

  1. Tons of wash water required per day. a. 252 c. 164 b. 50 d. 187
  2. Tung meal containing 55% oil is to be extracted at a rate of 4000 kg/hr using n-hexane containing 5% wt oil as solvent. A counter current multiple stage extraction system is to be used. The meal retains 2 kg solvent per kg of oil free meal while the residual charge contains 0.11 kg oil per kg oil free meal while the product is composed of 15 weight percent of oil. The theoretical number of stages is a. 4 c. 3 b. 5 d. 6 For numbers 1 7 to 1 8 : One thousand pounds of roasted copper ore containing 10 percent CuSO 4 , 85 percent insoluble gangue and 5 percent moisture is to be extracted by washing it three times with 2000-lb batches of fresh water. It has been found that the solids retain 0. lb of solution per pound of gangue.
  3. What is the percent CuSO 4 of the final underflow sludge after three washings? a. 0.13% c. 3.12% b. 6.54% d. 8.90%
  4. What is the percent recovery? a. 75.5% c. 85.1% b. 90.8% d. 97. 9 %
  5. Which of the following is the most commonly used leaching solvent in vegetable oil industry? a. phenol c. furfural b. hexane d. liquid SO 2
  6. Leaching of sugar from sugar beets is done using a. hot water c. dilute H 2 SO 4 b. hexane d. lime water
  7. In a counter-current extractor, as the axial mixing increases, the extraction efficiency a. increases b. decreases c. remains unchanged d. depends on the pressure of the system\
  8. Bollman extractor a. is a static bed leaching equipment. b. is used for extraction of oil from oilseed. c. is a centrifugal extractor. d. employs only counter-current extraction.
  9. Radioactive nuclear waste is treated in a. mixer-settler extractor b. rotating-disc contactor c. pulsed column extractor d. Bollman extractor

Liquid-Liquid Extraction

  1. Acetic acid will be most economically separated from a dilute solution of acetic acid in water by a. solvent extraction c. continuous distillation b. evaporation d. absorption
  2. Liquid-liquid extraction is based on the differences in a. solubility c. partial pressure b. specific volume d. viscosity
    1. The distribution coefficient of solute A between solvents B and S is given by Y = 2.5X where Y = mass fraction of A / mass of S in extract and X = mass fraction of A / mass fraction of B in raffinate. S and B are mutually immiscible. A solution containing 25% A in B is to be extracted in a single stage contact with a recovery of 80%. The amount of S in kg required per 100 kg of solution is nearly a. 100 c. 120 b. 150 d. 200
    2. A liquid mixture of acetaldehyde and toluene contains 8 lb of acetaldehyde and 90 lb of toluene. Part of the acetaldehyde in this solution is to be extracted using pure water as the extracting agent. The extraction is to be performed in two stages, using 25 lb of fresh water for each stage. The raffinate layer from the first stage is treated by fresh water in the second stage. The extraction takes place at 17^0 C and the equilibrium equation Y=2.2X may be employed. Assuming toluene and water is immiscible, what would be the weight percent of acetaldehyde in a mixture of the extracts from both stage if each of the extraction were theoretically perfect? a. 8.96% c. 9.33% b. 7.10% d. 5.52%
    3. The solubility of iodine per unit volume is 200 times greater in ether than in water at a particular temperature. If an aqueous solution of iodine, 30 ml in volume and containing 2 mg of iodine is shaken with 30 ml of ether and the ether is allowed to separate, what quantity of iodine remains in the water layer? a. 9.95x10-^3 mg c. 8.86 x10-^3 mg b. 6.05x10-^3 mg d. 5.40 x10-^3 mg
    4. What quantity of iodine remains in the water layer if only 3 ml of ether is used? a. 0.086 mg c. 0.095 mg b. 0.072 mg d. 0.063 mg
    5. How much iodine is left in the water layer if the extraction in ( 29 ) is followed by a second extraction, again using 3 ml of ether? a. 4.53x10-^3 mg c. 2.09 x10-^3 mg b. 1.37x10-^3 mg d. 2.88 x10-^3 mg
    6. Which method is more efficient, a single large washing or repeated small washing? a. single large washing b. repeated small washing c. both a and b d. either a or b
    7. A solution of solute (A) in diluent (B) is mixed with solvent (S). The component (B) is slightly soluble in (S). The resulting extract will be a. rich in S, poor in B, poor in A b. poor in S, rich in B, poor in A c. rich in S, rich in B, rich in A d. rich in S, poor in B, rich in A For numbers 33 to 3 4 : A solution of 5% acetaldehyde in toluene is to be extracted with water in a five stage concurrent unit. If 25 kg water per 100 kg of feed is used, calculate the following:

SEPARATION PROCESSES

CHEMICAL ENGINEERING PRINCIPLES

  1. The mass of acetaldehyde extracted if the equilibrium relation is given by: kg acetaldehyde per kg water = 2.20 (kg acetaldehyde per kg toluene). a. 4.49 kg / 100 kg feed c. 3.36 kg / 100 kg feed b. 1.11 kg / 100 kg feed d. 2.98 kg / 100 kg feed
  2. The final concentration a. 0.89% c. 0.54% b. 0.67% d. 0.33%
  3. To plan a liquid–liquid extraction we need to know the solute’s distribution ratio between the two phases. One approach is to carry out the extraction on a solution containing a known amount of solute. After extracting the solution, we isolate the organic phase and allow it to evaporate, leaving behind the solute. In one such experiment, 1.235 g of a solute with a molar mass of 117. g/mol is dissolved in 10.00 mL of water. After extracting with 5. mL of toluene, 0.889 g of the solute is recovered in the organic phase. How many extractions will we need to recover 99.9% of the solute? a. 5 c. 8 b. 6 d. 4 For numbers 3 6 to 3 7 : By extraction with amyl acetate, Penicillin F is recovered from an aqueous fermentation broth using 6 volumes of solvent per 100 volumes of the aqueous phase. At pH = 3.2, the distribution coefficient KD is 80.
  4. What fraction of the penicillin would be recovered in a single ideal stage? a. 77% c. 83% b. 65% d. 92%
  5. What would be the recovery with two-stage extraction using fresh solvent in both stages? a. 88% c. 75% b. 97% d. 69% For numbers 38 to 40 : Benzoic acid is 9 times more soluble in chloroform than in water. The percent benzoic acid that will remain from a water solution of benzoic acid if
  6. Equal quantity of chloroform and water is used is a. 10% c. 15% b. 20% d. 30%
  7. Twice as much as chloroform as water is used a. 2.6% c. 3.5% b. 5.3% d. 6.0%
  8. If extraction as in Problem 3 8 were followed by an extraction as in Problem 39 is a. 0.53% c. 0.63% b. 0.35% d. 0.73%
  9. The solvent used in liquid extraction should not have high latent heat of vaporization, because a. the pressure drop and hence the pumping cost will be very high. b. it cannot be recovered by distillation. c. its recovery cost by distillation may be prohibitively high. d. it will decompose while recovering by distillation.
    1. Solvent extraction is the terminology applied to the liquid-liquid extraction, which is preferred for the separation of the components of liquids, when a. extracting solvent is cheaply & abundantly available. b. one of the liquid components is heat sensitive. c. viscosity of liquid components is very high. d. one of the liquid components has very high affinity towards the solvent.
    2. In a counter-current liquid extractor a. both liquids flow at fixed rate. b. both liquids can have any desired flow rate. c. only one of the liquids may be pumped at any desired rate. d. liquid's flow rate depends upon the temperature and pressure.
    3. A coalescer in a mixer-settler liquid-liquid extraction column a. comprises of thin bed of substances of extended surface having high porosity. b. helps in increasing the bubble size entering the settler. c. helps in increasing the settling rate of the bubbles. d. all of these
    4. Antibiotics are best handled in a a. Podbielniak extractor b. rotating disc contactor c. sieve tray contractor d. pulsed column extractor

Distillation

  1. Which of the following solutions will follow Raoult's law most closely? a. A solution of benzene, toluene and oxylene b. 35% solution of camphor in water c. 35% solution of NH 3 in water d. A solution of polar organic compounds (not of homologs of a series).
  2. Calculate the equilibrium compositions of the liquid and the vapor phases for the mixture of methyl alcohol in water at a temperature of 50^0 C and under a pressure of 40 kPa. Assume that both the liquid and the vapor behave ideally. At 50^0 C, the vapor pressure of methyl alcohol is 53.32 kPa and that of water is 12.33 kPa. a. 67.5% methyl alcohol in liquid and 89.98% methyl alcohol in vapor b. 50.2% methyl alcohol in liquid and 77.60% methyl alcohol in vapor c. 61.1% methyl alcohol in liquid and 62.12% methyl alcohol in vapor d. 54.6% methyl alcohol in liquid and 94.33% methyl alcohol in vapor
  3. Determine the composition of the equilibrium vapor over a liquid mixture consisting of 10 mol % water, 50 mol % acetic acid and 40 mol % acetone at 80^0 C, assuming that the component obey Raoult`s law. The vapor pressures of components at 80^0 C are: water – 47.33 kPa, acetic acid – 27.32 kPa and acetone – 219. kPa. a. 2.55% water, 10.35% acetic acid and 87.10% acetone b. 4.45% water, 12.85% acetic acid and 82.70% acetone c. 3.50% water, 15.00% acetic acid and 81.50% acetone d. 5.60% water, 11.75% acetic acid and 82.65% acetone
  4. A binary mixture of two moles benzene and 8 moles of toluene will boil at a. 110 0 C c. 110 0 F b. 105 0 C d. 102 0 C

SEPARATION PROCESSES

CHEMICAL ENGINEERING PRINCIPLES

For numbers 72 to 74 : It is planned to feed continuously 100 mol per hour of a solution containing 80 mol of A and 20 mol of B to an externally fired kettle by which there is good agitation due to boiling. The residue and vapor will be withdrawn continuously, the vapor condensed, cooled and sent to storage. There is no return of residue or condensate to kettle, hence, this will be continuous simple distillation. It is planned to regulate the heat supply that D grams of distillate per hour will contain 72 mol of the more volatile component A which is five times more volatile than B.

  1. Calculate the mols of distillate per hundred moles of feed a. 85 c. 79 b. 62 d. 90
  2. What is the mole fraction of A in the distillate? a. 0.697 c. 0. b. 0.788 d. 0.
  3. What is the mole fraction of A in the residue? a. 0.533 c. 0. b. 0.375 d. 0.
  4. In distillation, the cooled liquid stream returned to the column to a cool plate or stage is called a. reboil c. feed b. reflux d. bottoms
  5. In a distilling column, the highest pressure will be at a. the top b. the bottom c. the feed plate d. between the feed plate and the top
  6. A heat transfer equipment to convert vapor to liquid is a/an a. evaporator c. condenser b. reboiler d. still
  7. A reboiler provides heat to the a. top b. the feed c. the intermediate reflux d. the bottom of a distilling column
  8. The temperature in distilling column, from bottom to top a. increases b. maximum c. decreases d. between minimum & maximum
  9. The theoretical minimum reflux ratio in distillation column is attained if the column has a. 1 plate c. 100 plates b. 10 plates d. infinite number of plates
  10. A benzene-toluene feed with (40 mol% benzene and 60 mol% benzene) to a distillation column is at a temperature of 20^0 C. The molar heat capacity of the feed is 159.2 kJ/kmol-K. Molar latent heats of vaporization of benzene and toluene are 30 813 and 33 325 kJ/kmol, respectively. The bubble point of the mixture is 95 (^0) C. The slope of the q line is closest to a. 0 c. 3. b. 1 d. - 3.
  11. If x co-ordinate of intersection point of feed line and rectifying sections operating line on equilibrium curve is same as the mole fraction of more volatile components in the feed, then the quality of feed is a. subcooled liquid c. saturated liquid b. saturated vapor d. superheated vapor
    1. One hundred kgmol/hr of 40 mol% benzene-toluene mixture is fractionated in a plate column at 1 atm. The overhead product must contain 95 mol% benzene and the bottoms must contain 95 mol% toluene. The feed is saturated liquid. If the reflux ratio is to be twice the minimum, determine the kgmol per hour of the overhead vapor? a. 38 c. 61 b. 43 d. 15 6
    2. A binary mixture with components A and B is to be separated in a distillation column to obtain 95 mol% A as the top product. The binary mixture has a constant relative volatility 𝛼𝐴𝐵 = 2. The column feed is a saturated liquid containing 50 mol% A. Under the usual simplifying assumptions such as constant molal overflow, negligible heat loss, ideal trays, the minimum reflux ratio for this separation is a. 1.7 c. 1. b. 1.6 d. 1. For numbers 85 to 86 : A binary feed mixture containing equimolar quantities of components S and T is to be distilled in a fractionating tower at atmospheric pressure. The distillate contains 96 mol % S. The q-line (feed line) intersects the equilibrium line at x' = 0.46 and y'= 0.66, where x' and y' are mole fraction s. Assume that the McCabe-Thiele method is applicable and the relative volatility is constant.
    3. The minimum reflux ratio is a. 1.6 c. 0. b. 1.5 d. 0.
    4. The feed is a. at dew point c. at bubble point b. superheated vapor d. partially vapor For numbers 87 to 89 : An ideal mixture of A and B is to be distilled continuously. If the relative volatility is constant at 1.75 and feed = saturated liquid with 50 mol% A feed rate = 200 lbmol/hr distillation composition = 90% A bottoms composition = 10% A
    5. Find the minimum number of theoretical stages a. 4.22 c. 7. 85 b. 6.85 d. 8.
    6. What is the minimum reflux ratio? a. 1.93 c. 2. b. 2.10 d. 1.
    7. The approximate minimum number of stages for as binary system with relative volatility of 2.35, fractionally distilled to yield compositions of 0.98 in the distillate and 0.045 in the bottoms is a. 4.8 c. 8. b. 7 d. 1 2
    8. In continuous rectification column is used to separate a binary mixture of A and B. Distillate in produced at 100 kgmol/hr containing 98 mole % A. The mole fractions of A in the liquid and in the vapor, x and y respectively, from two adjacent ideal plates in the enriching section are as follows x y 0.65 0. 0.56 0.

SEPARATION PROCESSES

CHEMICAL ENGINEERING PRINCIPLES

If the latent heat of vaporization is the same for all mixtures and if the feed is a saturated liquid, calculate the rate in the striping section in kg moles per hour a. 300 c. 200 b. 400 d. 500

  1. A rectification column is fed 100 kgmol/h of a mixture of 50 mol% benzene and 50 mol% toluene at 101.32 kPa abs pressure. The feed is liquid at the boiling point. The distillate is to contain 90 mol% benzene and the bottoms 10 mol% benzene. The reflux ratio is 4.52:1. Calculate the number of theoretical trays using McCabe-Thiele method. a. 5 + reboiler c. 6 + reboiler b. 4 + reboiler d. 3 + reboiler
  2. As the reflux ratio decreases, the a. separation becomes more efficient. b. number of plates increases. c. column diameter increases. d. none of these.
  3. In a distillation column, with increase in the reflux ratio, the heat removed in the cooler a. increases. b. decreases. c. remains unaffected. d. and the heat required in reboiler decreases.
  4. Fenske's equation for determining the minimum number of theoretical stages in distillation column holds good, when the a. relative volatility is reasonably constant. b. mixture (to be separated) shows negative deviation from ideality. c. mixture (to be separated) shows positive deviation from ideality. d. multicomponent distillation is involved.
  5. Inside the distillation column, the a. driving force for the vapor flow is the pressure drop. b. liquids are not always at their bubble points. c. pressure increases gradually from bottom to the top of the column. d. none of these
  6. On moving the feed line (q-line) from saturated liquid feed (vertical position) to saturated vapor feed (horizontal feed), if the slope of both the operating lines are to be increased, then it will result in a. greater degree of separation with a fixed number of trays b. increased reboiler load c. increased reflux ratio d. none of these
  7. In case of binary distillation, increasing the reflux ratio above optimum does not result in the increase of a. area between operating line and 45° diagonal x-y diagram b. condenser and reboiler surfaces c. tower cross-section d. none of these
  8. Overall efficiency of the distillation column is a. the ratio of number of ideal plates to actual plates b. the ratio of number of actual plates to ideal plates c. same as the Murphree efficiency d. always more than the point efficiency
    1. Pick out the correct statement. a. Ponchon-Savarit method is more accurate than McCabe- Thiele method to determine the number of theoretical stages required for the separation of non-ideal binary system by distillation. b. A sharp decrease in pressure drop is an indication of flooding in a distillation column. c. Solvent used in extractive distillation should be of high volatility. d. Flash distillation is suitable for separating components which have very close boiling temperature.
    2. Pick out the correct statement. a. The slope of the stripping line is always less than unity. b. For a given separation in a binary distillation column, with increase in reflux ratio (above the minimum reflux ratio), the fixed cost of the distillation column first increases and then decreases. c. In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux. d. Kremsor-Brown-Souder's equation is used to calculate the efficiency of a plate tower.
    3. Design calculation for multiple component distillation is done by a. Ponchon-Savarit method b. Mccabe-Thiele method c. enthalpy concentration method d. tray to tray calculations
    4. Pick out the wrong statement: a. Reboiler is not used in open steam distillation. b. The separation of solutes of different molecular sizes in a liquid solution by use of a suitable membrane is called dialysis. c. Freeze drying is used for the drying of fish. d. Fenske-Underwood equation is used for calculating theoretical number of plates in a distillation column at normal operating reflux condition.
    5. In extractive distillation, solvent is a. added to alter the relative volatility of the mixture. b. of high volatility. c. present in overhead stream. d. of high viscosity to give high tray efficiency.
    6. Solvent used in extractive distillation a. is of low volatility. b. forms a low boiling azeotrope. c. forms a high boiling azeotrope. d. does not alter the relative volatility of the original components.
    7. Pick out the wrong statement. a. Critical moisture content is not a property of the material itself. b. A sharp increase in pressure drop gives an indication of the flooding in a distillation column. c. Separation of components is not possible in liquid extraction, if selectivity is unity. d. Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum.
    8. Azeotropic distillation is employed to separate a. constant boiling mixture b. high boiling mixture c. mixture with very high relative volatility d. heat sensitive materials
    9. The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is a. more b. less c. same d. either more or less; depends on the system

CHEMICAL ENGINEERING THERMODYNAMICS

CHEMICAL ENGINEERING PRINCIPLES

Dimensions and Units For numbers 1 to 3 : Compare the costs of electricity at 1 p per kWh and gas at 15 p per therm.

  1. How many MJ in 1 kWh? a. 1.8 MJ c. 2.2 MJ b. 3.6 MJ d. 4.5 MJ
  2. What is the cost of electricity per MJ? a. 0.28 c. 0. b. 0.36 d. 0. 50
  3. What is the cost of gas per MJ? a. 0.28 c. 0. b. 0.36 d. 0.
  4. A piece of chocolate cake contains about 400 Calories. A nutritional Calorie is equal to 1000 calories (thermochemical calories). How many 8-inch high steps must a 180-lb man climb to expend 400 Cal from the piece of cake? a. 10 3 steps c. 10 3 0 steps b. 10 3 00 steps d. 10 3 000 steps For numbers 5 to 8 : A gas is confined in a 0.47 m diameter cylinder by a piston, on which rests a weight. The mass of the piston and weight together is 150 kg. The local gravity acceleration is 9.813 m/s^2 , the atmospheric pressure is 101.57 kPa.
  5. What is the force in Newtons exerted on the gas by the atmosphere, the piston and the weight, assuming no friction between the piston and cylinder? a. 1.91 x10^4 N c. 2.03 x10^4 N b. 1.56 x10^4 N d. 2.28 x10^4 N
  6. What is the pressure of the gas in kPa? a. 105 kPa c. 110 kPa b. 128 kPa d. 117 kPa
  7. If the gas in the cylinder is heated, it expands, pushing the piston and the weight upward. If the piston and weight are raised 0.83 m, what is the work done by the gas in kJ? a. - 16 kJ c. - 11 kJ b. 16 kJ d. 11 kJ
  8. What is the change in potential energy of the piston and weight? a. 1.8 kJ c. 1.9 kJ b. 1.5 kJ d. 1.2 kJ For numbers 9 to 12 : Calculate the work (J) done by a sample of 0.10 mol Ne gas that expands isothermally from 0.6 L to 1.2 L at 0oC according to the following conditions:
  9. against a constant external pressure of 0.9 atm. a. 7 c. 151 b. 55 d. 157
  10. against a variable pressure which varies with volume according to the expression PVn^ = k, and with the given data: Px10^3 (atm) 194 134 100 70 V (L) 0.60 0.80 1.0 1. a. 7 c. 151 b. 55 d. 157
    1. reversibly assuming gas is ideal a. 7 c. 151 b. 55 d. 157
    2. reversibly assuming gas obeys van der Waals equation of state (a=0.86 Pa-m^6 - mol-^2 and b = 3.18 x10-^5 m^3 - mol-) a. 7 c. 151 b. 55 d. 157 First Law of Thermodynamics
    3. Which law is the basis for the manufacture of thermometers? a. Boyle’s Law c. Zeroth Law of Thermodynamics b. Raoult’s Law d. Carnot’s Principle For numbers 14 to 16 : How many degrees of freedom has each of the following systems?
    4. Liquid water in equilibrium with its vapor a. one c. two b. three d. four
    5. Liquid water in equilibrium with a mixture of water vapor and nitrogen. a. one c. two b. three d. four
    6. A liquid solution of alcohol in water in equilibrium with its vapor. a. one c. two b. three d. four
    7. Energy is added to the water as work but is extracted from the water as heat was performed by a. Van ness c. Joule b. Fitzer d. Smith
    8. In Joule’s experiment, an insulated container contains 20 kg of water initially at 25^0 C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9. m/s^2. Neglecting the heat capacity of agitator, calculate the temperature of water in 0 C. a. 390 C c. 280 C b. 450 C d. 340 C
    9. These properties depend on the current state of the system and not on how the system reaches that state. a. path functions c. excess property b. state functions d. all of these
    10. Which of the following statement is correct? a. The standard heat of formation of an element is negative. b. Since △H = △U + △PV and can never be equal to △U. c. Q and W are state functions. d. Q + W is a state function.
    11. The amount of heat absorbed when CO 2 gas reacts with a solid CaO to form solid CaCO 3 is measured in a bomb calorimeter at constant volume. The data obtained give a direct measure of a. △U c. △H b. V△P d. Cp
    12. For a constant pressure reversible process, the enthalpy (∆H) change of the system is a. C vdT c. CpdT b. ∫CpdT d. ∫CvdT
    13. Cv is given by a. (∂U/ ∂T)v c. (∂U/∂V)T b. (∂U/∂P)v d. (∂V/ ∂T)P

CHEMICAL ENGINEERING THERMODYNAMICS

CHEMICAL ENGINEERING PRINCIPLES

For numbers 2 4 to 2 6 : A gas initially at 15 psia and 2 ft^3 undergoes a process to 90 psia and 0.6 ft^3 , during which the enthalpy increases by 15.5 BTU; Cv=2. BTU/lb-R. Determine

  1. ∆U a. 12.2 BTU c. 13.3 BTU b. 11.1 BTU d. 10.0 BTU
  2. Cp in BTU/lb-R a. 3.42 c. 4. b. 5.56 d. 2.
  3. R in in BTU/lb-R a. 0.54 c. 0. b. 0.61 d. 0.
  4. A gas is confined in a cylinder by a piston. The initial pressure of the gas is 7 bar, and the volume is 0.10 m^3. The piston is held in place by latches in the cylinder wall. The whole apparatus is placed in a total vacuum. What is the energy change of the apparatus if the remaining latches are removed so that the gas suddenly expands to double its initial volume, the piston striking other latches at the end of the process? a. - 10.13 kJ c. - 70 kJ b. 0 kJ d. cannot be determined
  5. One pound of a gas in a piston cylinder arrangement undergoes expansion from 500 psia to 50 psia. The initial volume of the gas is 3 ft^3 per lb. The variation of P and V is such that PV1.4^ is a constant. Calculate the change in internal energy if the work performed is equal to the amount of heat transferred to the surrounding. a. 0 BTU c. – 669 BTU b. 669 BTU d. - 776 BTU For numbers 29 to 31 : A container with an air tight piston is at a pressure of 100 psia and at a temperature of 70 0 F. The piston moves up when 100 BTU of heat is transferred at a constant pressure and the volume changes from 0.5 ft^3 to 2.0 ft^3. Assuming perfect gas behavior, calculate the following:
  6. The change in internal energy a. 84 BTU c. 60 BTU b. 72 BTU d. 55 BTU
  7. The final temperature in 0 F a. 1660 c. 1220 b. 1440 d. 1330
  8. The heat capacity of the process, Cp in BTU/R a. 0.0537 c. 0. b. 0.0416 d. 0.
  9. A group of 50 persons attended a secret meeting in a room which is 12 m by 10 m long and a ceiling of 3 m. The room is completely sealed off and insulated. Each person gives off 150 kcal per hour of heat and occupies a volume of 0.2 m^3. The room has an initial pressure of 101.3 kPa and temperature of 16^0 C. Calculate the room temperature after 10 minutes in 0 C. a. 25 c. 36 b. 33 d. 29 For numbers 33 to 35: Five hundred kilograms per hour of steam drives a turbine. The steam enters the turbine at 44 atm and 450^0 C at a linear velocity of 60 m/s and leaves at a point 5 m below the turbine inlet at atmospheric pressure and a velocity of 360 m/s. The turbine delivers shaft work at a rate of 70 kW, and the heat loss from the turbine is estimated to be 10^4 kcal/hr. Calculate the following:
    1. Change in kinetic energy a. 8.75 kW c. 9.66 kW b. 4.32 kW d. 5.05 kW
    2. Change in potential energy a. - 3.33 x10-^3 kW c. - 6.81 x10-^3 kW b.-4.06 x10-^3 kW d. - 1.99 x10-^3 kW
    3. Specific enthalpy change associated with the process a. - 720 kJ/kg c. - 510 kJ/kg b. - 890 kJ/kg d. - 650 kJ/kg
    4. Air flows steadily at a rate of 0.5 kg/s through an air compressor, entering at 7 m/s speed, 100 kPa pressure and. 0.95 m^3 /kg specific volume, and leaving at 5 m/s, 700 kPa, and 0.19 m^3 /kg. The internal energy of the air leaving is 90 kJ/kg greater than of the air entering. Cooling water in the compressor jackets absorbs heat from the air at a rate of 58 kW. Compute the work in kW. a. 211 kW c. 122 kW b. 112 kW d. 212 kW For numbers 3 7 to 3 8 : Steams flows at steady state through a converging insulated nozzle, 25 cm long and with an inlet diameter of 5 cm. At the nozzle entrance, the temperature and pressure are 325^0 C and 700 kPa, and the velocity is 30 m/s. At the nozzle exit, the steam temperature and pressure are 240^0 C and 350 kPa. Property values are: H 1 = 31125.5 kJ/kg H 2 = 2945.7 kJ/kg
    5. What is the velocity of the steam at the nozzle exit? a. 578 m/s c. 756 m/s b. 325 m/s d. 149 m/s
    6. What is the exit diameter? a. 1.33 cm c. 1.60 cm b. 1.49 cm d. 1.25 cm For numbers 39 to 40 : Air flows steadily and adiabatically through a horizontal straight pipe. The air enters the pipe at an absolute pressure of 100 psia, a temperature of 100^0 F, and a linear velocity of 10 ft/sec. The air leaves at 2 psia.
    7. What is the temperature of the leaving air? a. 60^0 F c. 80^0 F b. 70^0 F d. 50^0 F
    8. What is the velocity of the leaving air? a. 482 fps c. 345 fps b. 161 fps d. 229 fps Volumetric Properties of Pure Fluids
    9. Equation which relates pressure, volume, and temperature of a gas is called a. Equation of state b. ideal gas equation c. Gibbs Duhem equation d. all of these
    10. The equation, PV = nRT is best obeyed by gases at a. low pressure and high temperature b. high pressure and low temperature c. low pressure and low temperature d. high pressure and high temperature
    11. Compressibility factor of a gas is a. not a function of pressure b. not a function of its nature c. not a function of its temperature d. unity, if it follows PV = nRT

CHEMICAL ENGINEERING THERMODYNAMICS

CHEMICAL ENGINEERING PRINCIPLES

For numbers 67 to 69 : Five kilograms of carbon tetrachloride undergo a mechanically reversible, isobaric change of state at 1 bar during which the temperature changes from 0^0 C to 20^0 C. The properties for liquid carbon tetrachloride at 1 bar and 0 0 C may be assumed independent of temperature: β = 1.2x10-^3 /K, CP = 0.84 kJ/kg-K and ρ = 1590 kg/m^3. Determine the following:

  1. ΔV a. 8x10-^5 m^3 c. 6 x10-^5 m^3 b. 2x10-^5 m^3 d. 5x10-^5 m^3
  2. W a. - 5 J c. - 8 J b. - 2 J d. - 4 J
  3. Q a. 76 kJ c. 65 kJ b. 52 kJ d. 84 kJ
  4. ΔU a. 67.82 kJ c. 90.01 kJ b. 83.99 kJ d. 55.64 kJ
  5. For liquid water the isothermal compressibility is given by:

c V (P + b) where c and b are functions of temperature only. If 1 kg of water is compressed isothermally and reversibly from 1 to 500 bar at 600 C, how much work is required? At 60^0 C, b=2,700 bar and c=0.125 cm^3 /g. a. 516 J c. 289 J b. 403 J d. 772 J Second Law of Thermodynamics

  1. A central power plant, rated at 800 000 kW, generates steam at 585 K and discards heat to a river at 295 K. If the thermal efficiency of the plant is 70% of the maximum possible value, how much heat is discarded to the river at rated power? a. 1.5x10^3 MW c. 2.3 x10^3 MW b. 3.0 x10^3 MW d. 4.9 x10^3 MW For numbers 73 to 74 : A nuclear power plant generates 750 MW; the reactor temperature is 315^0 C and a river with water temperature of 20^0 C is available.
  2. What is the minimum rate at which heat must be discarded to the river? a. 680 MW c. 420 MW b. 330 MW d. 745 MW
  3. If the actual thermal efficiency of the plant is 60% of the maximum, what is the temperature rise in 0 C of the river if it has a flow of 165 m^3 s-? a. 4.0 c. 3. b. 2.5 d. 1. For numbers 75 to 77 : A heat engine operating at a Carnot cycle between 1540^0 F and 400 F rejects 250 BTU/lb of working fluid to the sink.
  4. What is the work produced by the heat engine? a. 190 BTU/lb c. 560 BTU/lb b. 350 BTU/lb d. 750 BTU/lb
    1. What is the Carnot efficiency? a. 40% c. 92% b. 75% d. 66%
    2. What is the maximum entropy change for any process in the cycle? a. 0.125 BTU/lb-R c. 0.375 BTU/lb-R b. 0.500 BTU/lb-R d. 0.224 BTU/lb-R
    3. An inventor claims to have a cyclic engine which exchanges heat with reservoirs at 25^0 C and 250^0 C, and which produces 0.45 kJ of work for each kJ of heat extracted from the hot reservoir. Is the claim believable? a. Yes b. No
    4. An inventor has devised a complicated non-flow process in which 1 mol of air is the working fluid. The net effects of the process are claimed to be:  A change in state of the air from 250^0 C and 3 bar to 80^0 C and 1 bar.  The production of 1800 J of work.  The transfer of an undisclosed amount of heat to a heat reservoir at 30^0 C. Determine whether the claimed performance of the process is consistent with the second law. Assume that air is an ideal gas for which Cp = (7/2)R. a. Yes b. No
    5. Consider A (l, 75^0 C)  A (^) (g, 155^0 C) which is carried out at constant pressure. The total S for this process is found to be 75.0 J/mol-K. For A (l) and A (g), the Cp are 75 J/mol-K and 29 J/mol-K, respectively, and are not independent on temperature. Calculate Hvap for A (l) at 125^0 C (boiling point). a. 2.5x10^4 J c. 2.5x10-^4 J c. 5.2x10^4 J d. 5.2x10-^4 J For numbers 81 to 83 : A 40-kg steel casting (Cp=0.5 kJ/kg-K) at a temperature of 450^0 C is quenched in 150 kg of oil (Cp=2.5 kJ/kg-K) at 25^0 C. if there are no heat losses, what is the change in entropy of
    6. The casting a. - 16.33 kJ/K c. - 26.13 kJ/k b. +16.33 kJ/K d. +26.13 kJ/k
    7. The oil a. - 16.33 kJ/K c. - 26.13 kJ/k b. +16.33 kJ/K d. +26.13 kJ/k
    8. Both considered together a. 9.8 kJ/K c. 0 kJ/K b. - 9.8 kJ/K d. 43 kJ/K
    9. Methane gas at 550 K and 5 bar undergoes a reversible adiabatic expansion to 1 bar. Assuming methane to be an ideal gas at these conditions, find its final temperature. Cp / R = 1.702 + 9.081x10-^3 T – 2.164 x10-^6 T^2. a. 411 K c. 389 K b. 465 K d. 307 K For numbers 85 to 87 : Hydrogen, initially at 15 psia and 80^0 F, is compressed at the rate of 20 cfm in a hot environment to a pressure of 75.3 psig. The details of the process are unknown but it us estimated the heat enters at the rate of 20 BTU/min. For a change of entropy of 0.0268 BTU/min-R. Determine:

CHEMICAL ENGINEERING THERMODYNAMICS

CHEMICAL ENGINEERING PRINCIPLES

  1. The final temperature. a. 660 R c. 970 R b. 820 R d. 710 R
  2. The work if the system is non-flow. a. 2.14 hp c. 4.69 hp b. 3.33 hp d. 5.02 hp
  3. The work if the system is steady flow. a. 246 BTU/min c. 188 BTU/min b. 257 BTU/min d. 1 3 5 BTU/min Heat Effects
  4. The difference between the heat of combustion of methane at constant pressure and at constant volume at 27^0 C when liquid water forms is a. – 1192.2 cal c. 1257.44 cal b. – 2314.5 cal d. – 1257.44 cal
  5. At 90^0 C, the vapor pressure of acetic acid is 293 mmHg and its vapor pressure at 100^0 C is 417mmHg. Calculate the normal boiling point of acetic acid. a. 271.4 K c. 298.2 K b. 391.3 K d. 303.0 K
  6. An ice skating rink contains ice at - 100C. Calculate the pressure than an ice skate blade must exert to allow smooth ice skating at this temperature. Assume that ΔHfusion= 1440 cal/mol. ρliquid = 1. g/ml and ρice = 0.917 g/ml. a. 10x10^3 psi c. 20x10^3 psi b. 15x10^3 psi d. 25x10^3 psi
  7. Calculate the heat required to raise the temperature 1 mol of methane from 260 to 600^0 C in a steady flow process at a pressure sufficient low that methane may be considered as ideal gas. a. 19800 J c. 22700 J b. 10100 J d. 25400 J For numbers 92 to 93 : A reversible compression of 1 mol of an ideal gas in piston/cylinder device results in a pressure increase from 1 bar to P 2 and a temperature increase from 400 K to 950 K. the path followed by the gas during compression is given by PV1.55^ = k, and the molar heat capacity is given by: Cp/R= 3.85 + 0.57x10-^3 T [T=K].
  8. Determine the heat transferred during the process. a. 5092 J c. 6478 J b. 3355 J d. 7216 J
  9. Calculate the final pressure. a. 11.45 bar b. 13.66 bar b. 10.05 bar d. 14.43 bar Applications of Thermodynamics to Flow Processes
  10. Determine whether water is compressed liquid, superheated vapor, saturated liquid, saturated vapor, or a mixture of saturated liquid and saturated vapor, in each case. If the state is determined to be a mixture, determine the quality. (i) At 10 MPa and an entropy of 3.3 kJ/kg-K (ii) At 320 0 C and 5.6 MPa (iii) With specific volume of 0.10 m^3 /kg at 1 MPa a. subcooled, superheated, mixture (0.50) b. mixture (0.40), superheated, subcooled c. superheated, mixture (0.60), subcooled d. subcooled, mixture (0.30), superheated
  11. Wet steam at 230 0 C has a density of 0.025 g/cm^3. Determine H. a. 2350 kJ/kg c. 1990 kJ/kg b. 3410 kJ/kg d. 4070 kJ/kg
  12. A steam turbine with rated capacity of 56 400 kW operates with steam at inlet conditions of 8600 kPa and 500^0 C, and discharges into a condenser at a pressure of 10 kPa. Assuming a turbine efficiency of 0.75, determine the mass rate of flow of the steam. a. 45 kg/s c. 37 kg/s b. 28 kg/s d. 59 kg/s For numbers 97 to 99 : Three pounds per second of steam expand in a turbine isentropically from 300 psia and 700^0 F to 200^0 F. Determine the following: S1: 1.6758 H1: 1368.9 V1: 2. Sfg: 1.4824 Hfg: 977.9 Vfg: 33. Sg2: 1.7764 Hg2: 1146 Vg2: 33.
  13. Quality of the exit steam. a. 88% c. 90% b. 93% d. 85%
  14. Steady flow work. a. 868 BTU/s c. 645 BTU/s b. 709 BTU/s d. 953 BTU/s
  15. Non-flow work. a. 842 BTU/s c. 698 BTU/s b. 755 BTU/s d. 904 BTU/s For numbers 100 to 10 2 : Water at 45^0 C and 10 kPa enters an adiabatic pump and is discharged at a pressure of 8600 kPa. Assume the pump efficiency to be 0.75. The following are properties for saturated liquid water at 450 C: V = 1.010 cm^3 /g, β = 425 x10-^6 /K and Cp = 4.178 kJ/kg-K. Calculate the following:
  16. Work of the pump a. 11.57 kJ/kg c. 12.05 kJ/kg b. 14.92 kJ/kg d. 13.66 kJ/kg
  17. Temperature change of the water a. 0.97 K c. 0.88 K b. 0.56 K d. 0.71 K
  18. Entropy change of the water a. 0.008 kJ/kg-K c. 0.005 kJ/kg-K b. 0.001 kJ/kg-K d. 0.009 kJ/kg-K

TRASNSPORT PROCESSES

CHEMICAL ENGINEERING PRINCIPLES

Heat Transfer

  1. The driving force in heat transfer is a. concentration gradient c. viscosity gradient b. temperature gradient d. thickness of the solid in question
  2. Thermal diffusivity of a material a. has the unit m^2 /sec. b. is defined as k/ρ x Cp. c. is the ratio of thermal conductivity to thermal capacity. d. all (a), (b) and (c).
  3. Under the same temperature gradient across various metal plates of the same thickness, the heat conducted per unit of surface area will be largest across a. lead c. iron b. copper d. nickel
  4. If a man touches two metals which were kept together at room temperature, why would one metal feel colder than the other a. one has a high heat transfer coefficient b. one has a high thermal conductivity c. one has a lower temperature d. one has a higher heat capacity
  5. Cork is a good insulator because it has a. free electrons b. atoms colliding frequency c. low density d. porous body
  6. The insulation ability of an insulator with the presence of moisture would a. increase c. remains unaffected b. decrease d. none of the above
  7. A furnace wall is constructed of firebrick 6 in thick. The temperature of the inside of the wall is 1300 0 F and the temperature of the outside of the wall is 175 0 F. If the mean thermal conductivity under these conditions is 0.17 BTU/hr-ft-^0 F, what is the rate of heat loss through 10 ft^2 of wall surface? a. 5700 BTU/hr c. 3825 BTU/hr b. 1070 kcal/hr d. 2354 kcal/hr For numbers 8 to 9 : A furnace is constructed with 0.20 m of firebrick, 0.10 m of insulating brick, and 0.20 m of building brick. The inside temperature is 1200 K and the outside temperature is 330 K. If the thermal conductivities are as shown in the figure, estimate the heat loss per unit area and the temperature at the junction of the firebrick and the insulating brick.
  8. The heat loss per unit area is a. 961 W/m^2 c. 1056 W/m^2 b. 1248 W/m^2 d. 1567 W/m^2
  9. The temperature at the junction of the firebrick and the insulating brick is a. 983 K c. 1063 K b. 1115 K d. 1472 K 10. A flat wall is to be constructed of firebrick, insulating brick, and building brick in series such that the heat loss will not exceed 250 BTU/hr-ft^2 when the hot face of the firebrick is 2000^0 F and the cold face of the building is 100^0 F. What minimum wall thickness is required? a. 22 in c. 3 in b. 9 in d. 18 in Data: k, BTU/hr- ft-^0 F brick thickness, in max allow, (^0) F fireclay brick 0.90 4.5 - insulating brick 0.12 3.0 1800 building brick 0.40 4.0 300 11. What actual heat loss will occur in Problem 10? a. 200 BTU/hr-ft^2 c. 240 BTU/hr-ft^2 b. 180 BTU/hr-ft^2 d. 160 BTU/hr-ft^2 12. The following data was obtained in a test on a flat-walled furnace the linings of which consist of a 4.5 in non-corrosive brick of unknown conductivity and the outer wall of 8 in clay brick, also of unknown conductivity. The temperature of the inner wall (flame side) was found to be 1105^0 F and that of the outer wall 365^0 F. This furnace was lagged with 2 in of magnesia (k=0.04) thermocouples inserted at various points and the following data taken. Temperature of inner wall (flame side) 13550 F Temperature at the junction of brick layers 12900 F Temperature at the junction of ordinary brick and magnesia 8900 F Temperature of the outer surface of magnesia 1900 F Calculate the % of heat loss that is saved by the lagging. a. 50% c. 37% b. 28% d. 44% 13. A hallow metal sphere is heated so that the inside wall temperature is 300^0 F. The sphere has an internal diameter of 6 inches and is 2 inches thick. What is the heat loss from the sphere if the outer surface is maintained at 212^0 F? The thermal conductivity of the metal is 8 BTU-ft/hr-ft^2 -^0 F? a. 7650 BTU/hr c. 1802 BTU/hr b. 4156 BTU/hr d. 5529 BTU/hr 14. A current of 250 amperes is passing through a stainless wire with diameter of 5.08 mm. The wire is 2.44 m long and has an electrical resistance of 0.0843 ohms. The outer surface is held constant at 154.6 0 C. The thermal conductivity of the wire is 22.5 W/m-K. The center temperature of the wire is a. 435 K c. 256 K b. 38 0 K d. 62 1 K 15. Heat transfer occurs by natural convection because change in temperature causes differences in a. viscosity c. thermal conductivity b. density d. heat capacity 16. The inner wall of a furnace is at a temperature of 700 0 C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W/m-K respectively. The ambient air is at 30 0 C and the heat transfer coefficient between the outer surface of wall and air is 20 W/m^2 - K. The rate of heat loss from the outer surface in W/m^2 is a. 165.4 c. 172. b. 167.5 d. 175.

TRASNSPORT PROCESSES

CHEMICAL ENGINEERING PRINCIPLES

For numbers 17 to 18 : A steel pipeline, 2 in-sch40, contains saturated steam at 121.1 0 C. The pipeline is insulated with 1 inch of asbestos (k=0.182 SI units). Assuming that the inside surface temperature of the pipe wall is at 121.1^0 C and the outer surface of the insulation is at 26.7^0 C.

  1. Calculate the heat loss (in Watts) for L=30.5 m. a. 5400 c. 4910 b. 4375 d. 3862
  2. How much steam in kg/hr is condensed due to the heat loss? a. 10.9 c. 8. b. 8.81 b. 9. For numbers 19 to 20 : Carbon tetrachloride, flowing at 19000 kg/hr is to be cooled from 850 C to 40^0 C in a double pipe heat exchanger using 13500 kg/hr of cooling water at 20^0 C. The overall heat transfer coefficient is 1500 W/m^2 - K. Assume specific heat of CCl 4 is 0.88 J/g-^0 C.
  3. Determine the area (in m^2 ) needed if flow is countercurrent. a. 5.7 c. 4. b. 1.9 d. 3.
  4. Determine the area (in m^2 ) needed if flow is parallel a. 7.8 c. 2. b. 3.9 d. 5.
  5. A cooling coil, consisting of a single length of tubing through which water is circulated, is provided in a reaction vessel, the contents of which are kept uniformly at 360 K by means of a stirrer. The inlet and outlet temperatures of the cooling water are 280 K and 320 K respectively. What would be the outlet water temperature if the length of the cooling coil were increased by 5 times? Assume the overall heat transfer coefficient to be constant over the length of the tube and independent of the water temperature. a. 429 K c. 358 K b. 370 K d. 465 K
  6. In an oil cooler, 216 kg/h of hot oil enters a thin metal pipe of diameter 25 mm. An equal mass of cooling water flows through the annular space between the pipe and a larger concentric pipe; the oil and water moving in opposite directions. The oil enters at 420 K and is to be cooled to 320 K. If the water enters at 290 K, what length of pipe will be required? Take coefficients of 1.6 kW/m^2 K on the oil side and 3.6 kW/m^2 K on the water side and 2 kJ/kg-K for the specific heat of the oil. a. 1.9 m c. 3.5 m b. 4.8 m d. 2.7 m
  7. The temperature of oil leaving a co-current flow cooler is to be reduced from 370 to 350 K by lengthening the cooler. The oil and water flowrates, the inlet temperatures and the other dimensions of the cooler will remain constant. The water enters at 285 K and oil at 420 K. The water leaves the original cooler at 310 K. If the original length is 1 m, what must be the new length? a. 1.86 m c. 3.33 m b. 2.52 m d. 4.50 m
  8. It is desired to warm an oil of specific heat 2.0 kJ/kg K from 300 to 325 K by passing it through a tubular heat exchanger containing metal tubes of inner diameter 10 mm. Along the outside of the tubes flows water, inlet temperature 372 K, and outlet temperature 361 K. The overall heat transfer coefficient from water to oil, based on the inside area of the tubes, may be assumed constant at 230 W/m^2 K, and 0.075 kg/s of oil is to be passed through each tube. The oil is to make two passes through the heater and the water makes one pass along the outside of the tubes. Calculate the length of the tubes required. a. 3 m c. 4 m b. 5 m d. 6 m
    1. Heat transfer in turbulent flow may be described by an empirical equation correlating a. Nusselt, Peclet, Prandtl numbers b. Nusselt, Prandtl, Stanton numbers c. Nusselt, Prandtl, Reynolds numbers d. Nusselt, Graetz, Schimdt numbers
    2. Air at 206.8 kPa and an average of 477.6 K is being heated as it flows through a tube of 25.4 mm inside diameter at a velocity of 7.62 m/s. The heating medium is 488.7 K steam condensing on the outside of the tube. Since the heat transfer coefficient of condensing steam is several thousand W/m^2 - K and the resistance of the metal wall is very small, it will be assumed that the surface wall temperature of the metal in contact with air is 488.7 K. Calculate the heat flux for an L/D
     > 60. a. 70 W/m^2 c. 60 W/m^2 b. 50 W/m^2 d. 80 W/m^2
    1. In a 1–1 shell and tube heat exchanger, steam is condensing on the shell side at TS °C, and the cold fluid is being heated on the tube side from t 1 °C to t 2 °C. The following equation relates t 2 to the other variables. Where ‘U’ is the overall heat transfer coefficient, ‘A’ is the heat transfer area, ‘W’ is the mass flow rate and ‘Cp’ is the heat capacity. The tube side coefficient is controlling and the tube side fluid is in turbulent flow. TS = 130°C, t 1 = 30°C, t 2 = 80°C. If the mass flow rate of the cold fluid is double while keeping all the other conditions it, find the new value of t 2 at steady state. a. 80^0 C c. 66^0 C b. 54^0 C d. 75^0 C
    2. When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by a. conduction c. radiation b. convection d. convection and radiation
    3. An ideal surface that absorbs all incident radiation, regardless of the wavelengths and direction and is also considered to be a perfect emitter is referred to as a a. gray body c. black body b. black hole d. pin hole
    4. In thermal radiation, for a black body a. α= 1 and ε is not equal to 1 b. α is not equal to 1 and ε= 1 c. α and ε are not equal to 1 d. α= 1 and ε= 1 where α is absorptivity and ε is emissivity. For numbers 31 to 32 : A bare horizontal pipe of 50 mm outside diameter is placed in a room where the air temperature is 290 K. Saturated steam at 415 K flows through the pipe. Using emissivity of 0.
    5. Estimate the heat transfer coefficient due to convection from the pipe to the room. a. 7.4 W/m^2 -^0 C c. 12.8 W/m^2 -^0 C b. 9.23 W/m^2 -^0 C d. 8.5 W/m^2 -^0 C
    6. What is the total heat loss per meter length of pipe from the steam to the room? a. 258 c. 5 64 b. 345 d. 305