An 8" ID pipe carries air at 80.0 ft/sec, 21.5 psi absolute and 80°F. How many pounds of air are flowing? The 8" pipe reduces to a 4" ID pipe and the pressure and temperature in the 4" pipe are 19.0 psi absolute and 48°F respectively. Find the velocity in the 4" pipe and compare the flows in ft3/sec in the two pipes.
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How does a photovoltaic cell generate electricity? How thick is the depletion width in a silicon solar cell? How can you calculate it?
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What are nanostructured materials in a PEM Fuel Cell?
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Identify the anode in a galvanic cell of copper and brass electrodes in standard solutions of their own ions. Identify the anode in a galvanic cell of a two-phase microstructure of a 50:50 Pb-Sn alloy. Identify the anode in a galvanic cell of a lead-tin solder on a Cast iron in seawater. Identify the anode in a galvanic cell of a brass bolt in a passive 430 stainless steel plate in seawater.
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A shell-and-tube heat exchanger uses cooling water in the tubes. There are two pressure gages installed on the the water side to the heat exchanger. Gage 1 (P1) is installed on the inlet water line, which is connected to the lower nozzle, while Gage (P2) is installed on the discharge water line, which is connected to the upper nozzle. Both pressure gages are very near the nozzle flanges. The pressure drop from each pressure gage to the exchanger channel is 1 psi. The vertical distance between the two pressure gages is 4’-8”. The current pressure difference in tube-side pressure drop (P1 – P2) is 6 psi. If the number of tube passes were changed from 2 to 4 (with no appreciable change in the exchanger tube count), the water side pressure drop P1 – P2 (psi) would be most nearly:
a. 34 c. 20
b. 28 d. 12
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Simulate the Spring Mass Damper System shown in Fig. Using MATLAB/Simulink, m being the mass of Vibrating System in Kg. c Being the coefficient of damping in N-sec/m, K being spring stiffness in N/m. For the values m=15kg C=100 N-sec/m k=200 N/m mx''+cx'+kx=f0sinwt
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How many grams of dipotassium succinate trihydrate (K2C4H4O4·3H2O, MW = 248.32 g/mol) must be added to 570.0 mL of a 0.0306 M succinic acid solution to produce a pH of 5.987? Succinic acid has pKa values of 4.207 (pKa1) and 5.636 (pKa2).
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Steam, initially at 15 bar and 250oC and stored in a rigid container, is reversibly compressed at constant temperature. During the compression, the steam receives 400 kJ/kg of work. Determine ?? and the final state of the steam. Thermodynamic data: NIST Chemistry WebBook (Thermophysical Properties of Fluid Systems)
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Is there a relationship between absorbance and polarity or wavelength and polarity? For example, chlorophyll is more polar than carotene and chlorophyll has higher lambda max of 661 than carotene with 449 lambda max.
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Lithium crystallizes in a bcc structure with an edge length of 3.509 Å.
Calculate its density. What is the approximate metallic radius of lithium in picometers?
(atomic weight of Li = 6.94)
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Part B
Which of the following is not a true statement?
Which of the following is not a true statement?
| Under SN2 and E2 conditions, primary alkyl halides form primarily substitution products. |
| Primary alkyl halides do not undergo SN1 and E1 reactions. |
| Under SN2 and E2 conditions, secondary alkyl halides form both substitution and elimination products. |
| Under SN2 and E2 conditions, tertiary alkyl halides form both substitution and elimination products. |
| Under SN1 and E1 conditions, tertiary alkyl halides form both substitution and elimination products. |
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Part C
Which of the following statements about an SN1 reaction is not correct?
Which of the following statements about an SN1 reaction is not correct?
| The rate-limiting step has a unimolecular transition state. |
| The mechanism has one step. |
| The reaction does not depend on the concentration of the nucleophile. |
| Tertiary alkyl halides are more reactive than secondary alkyl halides. |
| Products have both identical and inverted configurations compared with the reactant. |
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Part D
What product would be obtained from the SN1 reaction of 13CH2=CH-CH2-Br with methanol?
What product would be obtained from the SN1 reaction of 13CH2=CH-CH2-Br with methanol?
| CH2=CH-13CH2-OCH3 |
| CH2=13CH-CH2-OCH3 |
| 13CH2=CH-CH2-OCH3 |
| 13CH2=CH-CH2-OCH3 and CH2=CH-13CH2-OCH3 |
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Part E
Which of the following compounds would be the most reactive in an E2 reaction?
Which of the following compounds would be the most reactive in an E2 reaction?
| 7-bromo-1-octene |
| 8-bromo-1-octene |
| 5-bromo-1-octene |
| 6-bromo-1-octene |
| 4-bromo-1-octene |
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Part F
Which substrate forms a six-membered ring ether via an intramolecular nucleophilic substitution reaction?
Which substrate forms a six-membered ring ether via an intramolecular nucleophilic substitution reaction?
| Br-CH2-CH2-CH2-O- |
| Br-CH2-(CH2)5-CH2-O- |
| Br-CH2-(CH2)2-CH2-O- |
| Br-CH2-(CH2)3-CH2-O- |
| Br-CH2-(CH2)4-CH2-O- |
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Part G
Which of the following reaction sequences can be used to convert 2-butene into 2-butyne?
Which of the following reaction sequences can be used to convert 2-butene into 2-butyne?
| Br2/CH2Cl2, excess -NH2 |
| Br2/CH2Cl2, excess HO- |
| Br2/H2O, excess HO- |
| Br2/H2O, excess -NH2 |
| HBr, excess -NH2 |
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Part H
What reagents should be used to synthesize methyl isopropyl ether?
What reagents should be used to synthesize methyl isopropyl ether?
| isopropyl chloride and methoxide ion |
| methyl alcohol and isopropoxide ion |
| methyl chloride and methoxide ion |
| methyl chloride and isopropoxide ion |
| isopropyl chloride and methyl chloride |
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Part I
An SN2 reaction involves back-side attack. For which of the following reactants would you be able to demonstrate that back-side attack occurs?
An SN2 reaction involves back-side attack. For which of the following reactants would you be able to demonstrate that back-side attack occurs?
| a racemic mixture of (R) and (S)-2-bromobutane |
| 3-bromopentane |
| 2-bromopropane |
| 1-bromopentane |
| (R)-2-bromobutane |
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Part J
How does a change to a more polar solvent affect the reaction coordinate diagram for an SN2 reaction of an alkyl halide with a negatively charged nucleophile?
How does a change to a more polar solvent affect the reaction coordinate diagram for an SN2 reaction of an alkyl halide with a negatively charged nucleophile?
| The energy of the reactants is decreased slightly, and the energy of transition state is decreased significantly more. |
| The energy of reactants and the energy of the transition state decrease by about the same amount. |
| Good. The energy of reactants is decreased, and the energy of the transition state is decreased significantly less. |
| The energy of the reactants and the energy of the transition state increase by about the same amount. |
| The energy of the reactants is increased, and the energy of the transition state remains about the same. |
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Part K
What would be the major product formed from the E2 reaction between (CH3)2CH-CHF-CH2CH3 and hydroxide ion?
What would be the major product formed from the E2 reaction between (CH3)2CH-CHF-CH2CH3 and hydroxide ion?
| (CH3)2CH-CH=CH-CH3 |
| (CH3)2C=CH-CH2CH3 |
| (CH3)2CH-CH2-CH=CH2 |
| CH3-CH=CH-CH2CH3 |
| H2C=C(CH3)-CH=CH-CH3 |
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Part L
Which of the following alkyl halides will be the most reactive in an E2 reaction?
Which of the following alkyl halides will be the most reactive in an E2 reaction?
| 1-bromo-2-methylpentane |
| 1-bromo-2,2-dimethylpentane |
| 1-bromo-4-methylpentane |
| 2-bromo-3-methylpentane |
| 3-bromo-3-methylpentane |
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Part M
Which of the following statements is not correct?
Which of the following statements is not correct?
| An E1 reaction is favored by a strong base. |
| A primary alkyl halide will not undergo an E1 reaction. |
| A tertiary alkyl halide can undergo both E1 and E2 reactions. |
| An E2 reaction is a concerted reaction. |
| Secondary alkyl halides are more reactive than primary alkyl halides in E2 reactions. |
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Part N
Which of the following is not a true statement?
Which of the following is not a true statement?
| If there are two hydrogens bonded to the ? carbon, both E and Z isomers will be formed in an E2 reaction. |
| The major product of an E1 reaction will be the alkene that has the bulkiest groups on opposite sides of the double bond. |
| If there are two hydrogens bonded to the ? carbon, the major product of an E2 reaction will be the alkene that has the bulkiest groups on opposite sides of the double bond. |
| Only the E isomer is formed in an E2 reaction. |
| Both E and Z isomers will be formed in an E1 reaction. |
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Part O
What product will be formed from the reaction of cis-1-bromo-4-methylcyclohexane with methoxide ion?
What product will be formed from the reaction of cis-1-bromo-4-methylcyclohexane with methoxide ion?
| trans-1-methoxy-4-methylcyclohexane |
| trans-4-methylcyclohexanol |
| trans- and cis-1-methoxy-4-methylcyclohexane |
| trans- and cis-4-methylcyclohexanol |
| cis-1-methoxy-4-methylcyclohexane |
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Part P
Which of the following alkyl halides is the most reactive in an SN2 reaction?
Which of the following alkyl halides is the most reactive in an SN2 reaction?
| 1-bromo-2,3-dimethylpropane |
| 1-chlorobutane |
| 1-bromobutane |
| 1-bromo-2-methylpropane |
| 2-bromopropane |
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Part Q
Which of the following would be the best nucleophile in a protic solvent?
Which of the following would be the best nucleophile in a protic solvent?
| acetate ion |
| phenolate ion |
| methanol |
| methylamine |
| methoxide ion |
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Part R
Which of the following is not a true statement?
Which of the following is not a true statement?
| The concentration of the alkyl halide affects the rate of an SN1 reaction. |
| The nature of the leaving group affects the rate of an SN1 reaction. |
| The concentration of the alkyl halide affects the rate of an SN2 reaction. |
| The nature of the leaving group affects the rate of an SN2 reaction. |
| The nature of the nucleophile affects the rate of an SN1 reaction. |
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Part S
What is the product of the SN1 hydrolysis of (R)-3-chloro-3-methylheptane?
What is the product of the SN1 hydrolysis of (R)-3-chloro-3-methylheptane?
| (S)-3-methyl-3-heptanol |
| (R) and (S)-3-methoxy-3-methylheptanol |
| (R) and (S)-3-methyl-3-heptanol with slightly more of the R enantiomer |
| (R) and (S)-3-methyl-3-heptanol with slightly more of the S enantiomer |
| (R)-3-methyl-3-heptanol |
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Part T
If an alkyl halide undergoes both SN1 and SN2 reactions with methoxide ion in 75 percent methanol and 25 percent water, which of the following would increase the percentage of product produced by the SN2 reaction?
If an alkyl halide undergoes both SN1 and SN2 reactions with methoxide ion in 75 percent methanol and 25 percent water, which of the following would increase the percentage of product produced by the SN2 reaction?
| decreasing the concentration of the alkyl halide |
| changing the nucleophile to methanol |
| increasing the concentration of methoxide ion |
| decreasing the concentration of methoxide ion |
| increasing the concentration of the alkyl halide |
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A municipal wastewater treatment plant is designed for COD removal and nitrification. The wastewater characteristics and kinetic coefficients are described in the table below. The aeration tank DO concentration is 2.0 mg/L and MLSS concentration is 2500 mg/L. The temperature is 15C. Assume that the concentration of influent NH4-N that is nitrified accounts for 80% of influent TKN. Calculate the following parameters as a function of SRT (i.e., derive mathematical expressions of the following parameters as a function of SRT, respectively, and show your calculation in detailed steps), and plot them as a function of SRT by varying SRT from 3 to 20 days.
(a) Effluent COD concentration (mg/L);
(b) Effluent NH4-N concentration (mg/L);
(c) Aeration tank volume (m3);
(d) Hydraulic retention time t (hours);
(e) Solids production as kg TSS/d;
(f) Oxygen requirement as kg/d.
Wastewater characteristics
Flow rate = 20,000 m3/d
VSS = 200 mg/L
COD = 352 mg/L
TKN = 40 mg/L
nbVSS = 100 mg/L
Temperature = 15 oC TSS = 220 mg/L
Kinetic coefficients of heterotrophic bacteria at 20 C
µm=6 g VSS/g VSS d
Theta for µm = 1.07
Ks=20 mg COD/L
Theta for Ks= 1.00
Y=0.4 g VSS/g VSS
Theta for kd =1.04
kd=0.12 g VSS/g VSSd
fd=0.15 g VSS/g VSS
Kinetic coefficients of nitrification at 20 C
µnm=0.75 g VSS/g VSSd
Theta for µnm = 1.07
Kn=0.74 mg NH4-N/L
Theta for Kn = 1.053
Yn=0.12 g VSS/g NH4-N
Theta for kdn =1.04
kdn=0.08 g VSS/g VSSd
Theta for Ko = 1.00
Ko=0.5 mg O2/L
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1.A liquid fuel mixture contains 29.50 % hexane (C6H14), 17.70 % heptane (C7H16), and the rest octane (C8H18). What maximum mass of carbon dioxide is produced by the complete combustion of 10.0 kg of this fuel mixture? 2.Many home barbeques are fueled with propane gas (C3H8).What mass of carbon dioxide (in kg) is produced upon the complete combustion of 18.9 L of propane (approximate contents of one 5-gallon tank)? Assume that the density of the liquid propane in the tank is 0.621 g/mL. (Hint: Begin by writing a balanced equation for the combustion reaction.)
2.What mass of carbon dioxide (in kg) is produced upon the complete combustion of 18.9 L of propane (approximate contents of one 5-gallon tank)? Assume that the density of the liquid propane in the tank is 0.621 g/mL. (Hint: Begin by writing a balanced equation for the combustion reaction.)
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