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engineering
chemical engineering
Questions and Answers of
Chemical Engineering
A ventilation system has been designed for a large laboratory with a volume of 1100 m3. The volumetric flow rate of ventilation air is 700 m3/min at 22°C and 1 atm. (The latter two values may also
A gas leak has led to the presence of 1.00 mole% carbon monoxide in a 350-m3 laboratory.4 The leak was discovered and sealed, and the laboratory is to be purged with clean air to a point at which the
Ninety kilograms of sodium nitrate is dissolved in 110 kg of water. When the dissolution is complete (at time r = 0), pure water is fed to the tank at a constant rate m (kg/min), and solution is
A tracer is used to characterize the degree of mixing in a continuous stirred tank. Water enters and leaves the mixer at a rate of V (m3/min). Scale has built up on the inside walls of the tank, so
A 40.0-ft3 oxygen tent initially contains air at 68°F and 14.7psia. At a time t = 0 an enriched air mixture containing 35.0% v/v O2 and the balance N2 is fed to the tent at 68°F and 1.3 psig at a
A radioactive isotope decays at a rate proportional to its concentration. If the concentration of an isotope is C (mg/L), then its rate of decay may he expressed as rd [mg/ (L∙s)] = kC where k is a
A chemical reaction with stoichiometry A ? products is said to follow an nth-order rare law if A is consumed at a rate proportional to the nth power of its concentration in the reaction mixture. If
A gas-phase decomposition reaction with stoichiometry 2A ? 2B + C follows a second-order rate law (see Problem 11.14): rd [mo1/(m3?s)] = kC2A where CA is the reactant concentration in moUrn3. The
In an enzyme-catalyzed reaction with stoichiometry A → B, A is consumed at a rate given by an expression of the Michaelis—Menten form: where CA (mol/L) is the reactant concentration, and k1 and
Phosgene (COCl2) is formed by CO and Cl2 reacting in the presence of activated charcoal: CO + Cl2 ? COCl2?At T = 303.8 K the rate of formation of phosgene in the presence of 1 gram of charcoal is
A gas that contains CO2 is contacted with liquid water in an agitated batch absorber. The equilibrium solubility of CO2 in water is given by Henry’s law (Section 6.4b) CA = pA/HA where CA
A liquid-phase chemical reaction with stoichiometry A → B takes place in a semi batch reactor. The rate of consumption of A per unit volume of the reactor contents is given by the first-order rate
A kettle containing 3.00 liters of water at a temperature of 18°C is placed on an electric stove and begins to boil in four minutes.(a) Write an energy balance on the water, neglecting evaporation
An electrical coil is used to heat 20.0 kg of water in a closed well-insulated vessel. The water is initially at 25°C and 1 atm. The coil delivers a steady 2.50 kW of power to the vessel and its
An iron bar 2.00 cm x 3.00 cm x 10.0 cm at a temperature of 95°C is dropped into a barrel of water at 25°C. The barrel is large enough so that the water temperature rises negligibly as the bar
A steam coil is immersed in a stirred heating tank. Saturated steam at 7.50bar condenses within the coil, and the condensate emerges at its saturation temperature. A solvent with a heat capacity of
At 9:30 one morning, a graduate student measures 350 grams of liquid benzene at 20°C into a glass flask dirty enough that its contents cannot be seen, puts the open flask on a Bunsen burner, turns
A steam radiator is used to heat a 60-m3 room. Saturated steam at 3.0bar condenses in the radiator, and emerges as a liquid at the saturation temperature. Heat is lost from the room to the outside at
An immersed electrical heater is used to raise the temperature of a liquid from 20?C to 60?C in 20.0 mm. The combined mass of the liquid and the container is 250 kg, and the mean heat capacity of the
A 2000-liter tank initially contains 400 liters of pure water. Beginning at t = 0, an aqueous solution containing 1.00 g/L of potassium chloride flows into the tank at a rate of 8.00 L/s and an
The diagram below shows three continuous stirred tanks connected in series. The flow and mixing patterns in this system arc studied by dissolving 1500 g of a salt (S) in the first tank, filling each
The following chemical reactions take place in a liquid-phase batch reactor of constant volume V.A → 2B r1 [mol A consumed/ (L∙s)] = 0.100CAB → C r2 [mol C generated/(L∙s) = 0.200C2B where
A liquid mixture containing 70.0 mol of n-pentane and 30.0 mol of n-hexane initially at 46?C is partially vaporized at P = 1 atm in a single-stage distillation apparatus (Rayleigh still). The heat
The process descriptions, process flow diagrams, and technical data for processes used commercially in 38 chemical industries. For each of the following processes, draw a block-flow diagram of just
Explain in detail, using thermodynamic principles, why the mixing of pure chemicals to form a homogeneous mixture is a so called spontaneous process, while the separation of that mixture into its
Explain in detail, using the first and second laws of thermodynamics, why the separation of a mixture into essentially pure species or other mixtures of differing compositions requires the transfer
Compare the advantages and disadvantages of making separations using an ESA versus using an MSA.
Every other year, the magazine Hydrocarbon Processing publishes a petroleum-refining handbook, which gives process flow diagrams and data for more than 75 commercial processes.For each of the
Every other year, the magazine Hydrocarbon Processing publishes a petrochemical handbook, which gives process-flow diagrams and data for more than 50 commercial processes. For each of the following
The osmotic pressure, π, of sea water is given approximately by the expression π = RTc/M, where c is the concentration of the dissolved salts (solutes) in g/cm3 and M is the average
It has been shown that a liquid membrane of aqueous ferrous ethylenediaminetetraacetic acid, maintained between two sets of micro porous, hydrophobic, hollow fibers that are packed in a permeator
Explain the differences, if any, between adsorption and gas-solid chromatography.
In electrophoresis, explain why most suspended particles are negatively charged.
In field-flow fractionation, could a turbulent-flow field be used? Why or why not?
The feed to Column C3 of the distillation sequence in Figure is given in Table 1.5. However, the separation is to be altered so as to produce a distillate that is 95 mol% pure isobutene with a
Five hundred kmol/h of a liquid mixture of light alcohols containing, by moles, 40% methanol (M), 35% ethanol (E), 15% isopropanol (IP), and 10% normal propanol (NP) is distilled in a sequence of two
A mixture of ethanol and benzene is separated in a network of distillation and membrane separation steps. In one intermediate step, a near-azeotropic liquid mixture of 8,000 kg/h of 23 wt% ethanol in
The Prism gas permeation process developed by the Monsanto Company is highly selective for hydrogen when using hollow-fiber membranes of materials such as silicone-coated polysulphone. In a typical
Nitrogen gas can be injected into oil wells to increase the recovery of crude oil (enhanced oil recovery). Usually, natural gas is produced with the oil and it is desirable to recover the nitrogen
A mixture of ethylbenzene (EB) and the three isomers (ortho, meta, and para) of xylene is widely available in petroleum refineries. (a) Based on differences in normal boiling points, verify that the
When a mixture of ethanol and water is distilled at ambient pressure, the products are a distillate of ethanol and water of nearazeotrope composition (89.4 mol% ethanol) and a bottoms product of
A stream containing 7,000 kmol/h of water and 3,000 parts per million (ppm) by weight of ammonia at 350 K and 1 bar is to be processed to remove 90% of the ammonia. What type of separation operation
A light-hydrocarbon feed stream contains 45.4 kmol/h of propane, 136.1 kmol/h of isobutane, 226.8 kmol/h of n-butane, 181.4 kmol/h of isopentane, and 317.4 kmol/h of n-pentane. This stream is to be
The need to remove organic pollutants from wastewater is common to many industrial processes. Separation methods that may be considered are: (1) adsorption, (2) distillation, (3) liquid-liquid
Many waste gas streams in processing plants contain volatile organic compounds (VOCs), which must be removed. Recovery of the VOCs may be accomplished by several separation methods, including: (1)
Describe three methods suitable for the separation of air into nitrogen and oxygen.
An aqueous stream contains 5% by weight of magnesium sulfate. Devise a process, complete with a process-flow diagram, for the production of nearly pure magnesium sulfate from this stream.
Explain why the separation of a stream containing 10 wt% acetic acid in water might be more economical by liquid-liquid extraction with ethyl acetate than by distillation.
A hydrocarbon stream in a petroleum refinery is to be separated at 1,500 kPa into two products under the conditions shown below. Using the data given, compute the minimum work of separation, Wmin ,
In petroleum refineries, a mixture of paraffins and cycloparaffins is commonly reformed in a fixed-bed catalytic reactor to produce blending stocks for gasoline and aromatic precursors for making
Distillation column C3 in Figure separates stream 5 into streams 6 and 7, according to the material balance in Table 1.5. A suitable column for the separation, if carried out at 700kPa, contains 70
A spiral-wound, nonporous cellulose acetate membrane separator is to be used to separate a gas containing H2, CH4, and C2H6. The permeate will be 95 mol% pure H2 and will contain no ethane. The
Which of the following K-value expressions, if any, is (are) rigorous? For those expressions that are not rigorous, cite the assumptions involved. (a) Ki = ФiL/ФiV (b) Ki =
Experimental measurements of Vaughan and Collins [Ind. Eng. Chem., 34,885 (1942)] for the propane-isopentane system at 167°F and 147 psia show for propane a liquid-phase mole fraction of 0.2900 in
Mutual solubility data for the isooctane (1)/furfural (2) system at 25?C are [Chem. Eng. Sci., 6, 116 (1957)] Compute: (a) The distribution coefficients for isooctane and furfural (b) The relative
In petroleum refineries, streams rich in alkylbenzenes and alkylnaphthalenes result from catalytic cracking operations. Such streams can be hydrodealkylated to more valuable products such as benzene
A binary ideal-gas mixture of A and B undergoes an isothermal, isobaric separation at To, the infinite surroundings temperature. Starting with Eq. (4), Table 2.1, derive an equation for the minimum
The separation of isopentane from n-pentane by distillation is difficult (approximately 100 trays are required), but is commonly practiced in industry. Using the extended Antoine vapor pressure
Operating conditions at the top of a vacuum distillation column for the separation of ethylbenzene from styrene are given below, where the overhead vapor is condensed in an air cooled condenser to
Toluene can be hydrodealkylated to benzene, but the conversion per pass through the reactor is only about 70%. Consequently, the toluene must be recovered and recycled. Typical conditions for the
Measured conditions for the bottoms from a depropanizer distillation unit in a small refinery are given below. Using the data in Figure and assuming an ideal liquid solution (volume of mixing = 0),
Isopropanol, containing 13 wt% water, can be dehydrated to obtain almost pure isopropanol at a 90% recovery by azeotropic distillation with benzene. When condensed, the overhead vapor from the column
A hydrocarbon vapor-liquid mixture at 250?F and 500 psia contains N2, H2S, CO2, and all the normal paraffins from methane to heptane. Use Figure to estimate the K-value of each component in the
Acetone, a valuable solvent, can be recovered from air by absorption in water or by adsorption on activated carbon. If absorption is used, the conditions for the streams entering and leaving are as
Subquality natural gas contains an intolerable amount of nitrogen impurity. Separation processes that can be used to remove nitrogen include cryogenic distillation, membrane separation, and
Use the R-K equation of state to estimate the partial fugacity coefficients of propane and benzene in the vapor mixture of Example 2.5.
Use a computer-aided, steady-state simulation program to estimate the K-values, using the P-R and S-R-K equations of state, of an equimolar mixture of the two butane isomers and the four butane
The disproportionation of toluene to benzene and xylenes is carried out in a catalytic reactor at 500 psia and 950?F. The reactor effluent is cooled in a series of heat exchangers for heat recovery
For an ambient separation process where the feed and products are all nonideal liquid solutions at the infinite surroundings temperature, To, (4) of Table 2.1 for the minimum work of separation
The sharp separation of benzene and cyclohexane by distillation at ambient pressure is impossible because of the formation of an azeotrope at 77.6oC. K.C. Chao [Ph.D. thesis, University of Wisconsin
Benzene can be used to break the ethanol/water azeotrope so as to produce nearly pure ethanol. The Wilson constants for the ethanol(l)/benzene(2) system at 45oC are A12 = 0.124 and A21 = 0.523. Use
For the binary system ethanol(l)/isooctane(2) at 50?C, the infinite-dilution, liquid-phase activity coefficients are ?1? = 21.17 and ?2? = 9.84.(a) Calculate the constants A12 and All in the van Laar
A beaker filled with an equimolar liquid mixture of ethyl alcohol and ethyl acetate evaporates at O?C into still air at 101 kPa (1 atm) total pressure. Assuming Raoult's law applies, what will be the
An open tank, 10 ft in diameter and containing benzene at 25oC, is exposed to air in such a manner that the surface of the liquid is covered with a stagnant air film estimated to be 0.2 in, thick. If
An insulated glass tube and condenser are mounted on a reboiler containing benzene and toluene. The condenser returns liquid reflux so that it runs down the wall of the tube. At one point in the tube
Air at 25°C with a dew-point temperature of 0°C flows past the open end of a vertical tube filled with liquid water maintained at 25°C. The tube has an inside diameter of 0.83 in., and the liquid
Two bulbs are connected by a tube, 0.002 m in diameter and 0.20 m in length. Initially bulb 1 contains argon, and bulb 2 contains xenon. The pressure and temperature are maintained at 1 atm and
The diffusivity of toluene in air was determined experimentally by allowing liquid toluene to vaporize isothermally into air from a partially filled vertical tube 3 mm in diameter. At a temperature
An open tube, 1 mm in diameter and 6 in. long, has pure hydrogen blowing across one end and pure nitrogen blowing across the other. The temperature is 75°C.(a) For equimolar counterdiffusion, what
Some HC1 gas diffuses across a film of air 0.1 in. thick at 20°C. The partial pressure of HC1 on one side of the film is 0.08 atrn and it is zero on the other. Estimate the rate of diffusion, as mol
Estimate the diffusion coefficient for the gaseous binary system nitrogen (A) /toluene (B) At 25oC and 3 atm using the method of Fuller et al.
For the mixture of Example 3.3, estimate the diffusion coefficient if the pressure is increased to 100 atm using the method of Takahashi.
Estimate the diffusivity of carbon tetrachloride at 25oC in a dilute solution of:(a) Methanol,(b) Ethanol,(c) Benzene, and(d) n-Hexane by the method of Wilke-Chang and Hayduk-Minhas. Compare the
Estimate the liquid diffusivity of benzene (A) In formic acid(B) At 25°C and infinite dilution. Compare the estimated value to that of Example 3.6 for formic acid at infinite dilution in benzene.
Estimate the liquid diffusivity of acetic acid at 25oC in a dilute solution of:(a) Benzene,(b) Acetone,(c) Ethyl acetate, and(d) Water by an appropriate method. Compare the estimated values with the
Water in an open dish exposed to dry air at 25oC is found to vaporize at a constant rate of 0.04 g/h-cm2. Assuming the water surface to be at the wet-bulb temperature of ll.0°C, calculate the
Isopropyl alcohol is undergoing mass transfer at 35?C and 2 atm under dilute conditions through water, across a phase boundary, and then through nitrogen. Based on the date given below, estimate for
Experimental liquid-phase activity-coefficient data are given in Exercise 2.23 for the ethanol/benzene system at 45oC. Estimate and plot diffusion coefficients for both ethanol and benzene over the
Estimate the diffusion coefficient of NaOH in a 1-M aqueous solution at 25°C
Estimate the diffusion coefficient of NaCl in a 2-M aqueous solution at 18oC. Compare your estimate with the experimental value of 1.28 10-5 cm2/s.
Estimate the diffusivity of N2 in H2 in the pores of a catalyst at 300°C and 20 atm if the porosity is 0.45 and the tortuosity is 2.5. Assume ordinary molecular diffusion in the pores.
Gaseous hydrogen at 150 psia and 80°F is stored in a small, spherical, steel pressure vessel having an inside diameter of 4 in. and a wall thickness of 0.125 in. At these conditions, the solubility
A polyisoprene membrane of 0.8-pm thickness is to be used to separate a mixture of methane and H2. Using the data in able 14.9 and the following compositions, estimate the mass transfer flux of each
A 3-ft depth of stagnant water at 25oC lies on top of a 0.10-in. thickness of NaCl. At time < 0, the water is pure. At time = 0, the salt begins to dissolve and diffuse into the water. If the
A slab of dry wood of 4-in. thickness and sealed edges is exposed to air of 40% relative humidity. Assuming that the two unsealed faces of the wood immediately jump to an equilibrium moisture content
A wet, clay brick measuring 2 × 4 × 6 in. has an initial uniform moisture content of 12 wt%..At time = 0, the brick is exposed on all sides to .air such that the surface moisture content is
A spherical ball of clay, 2 in. in diameter, has an initial moisture content of 10 wt%. The diffusivity of water in the clay is 5 × 10–6 cm2/s. At time t = 0, the surface of the clay is brought
Estimate the rate of absorption of pure oxygen at 10 atm and 25°C into water flowing as a film down a vertical wall 1 m high and 6 cm in width at a Reynolds number of 50 without surface ripples.
For the conditions of Example 3.13, determine at what height from the top the average concentration of CO2 would correspond to 50% of saturation.
Air at 1 atm flows at 2 m/s across the surface of a 2-in.-long surface that is covered with a thin film of water. If the air and water are maintained at 25oC, and the diffusivity of water in air at
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