MCQOPTIONS
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MCQOPTIONS
This section includes 80 Mcqs, each offering curated multiple-choice questions to sharpen your Chemical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
The surface renewal frequency in Danckwerts' model of mass transfer is given by ( K L : mass transfer co-efficient) |
| A. | K L 2 . D A |
| B. | K L 2 . D A |
| C. | K L 2 / D A |
| D. | K L / D A 2 |
| Answer» D. K L / D A 2 | |
| 52. |
In a liquid-liquid extraction, 10 kg of a solution containing 2 kg of solute C and 8 kg of solvent A is brought into contact with 10 kg of solvent B. Solvent A and B are completely immiscible in each other whereas solute C is soluble in both the solvents. The extraction process attains equilibrium. The equilibrium relationship between the two phases is Y * = 0.9X, where Y * is the kg of C/kg of B and X is kg of C/kg of A. Choose the correct answer. |
| A. | The entire amount of C is transferred to solvent B. |
| B. | Less than 2 kg but more than 1 kg of C is transferred to solvent B. |
| C. | Less than 1 kg of C is transferred to B. |
| D. | No amount of C is tranferred to B. |
| Answer» B. Less than 2 kg but more than 1 kg of C is transferred to solvent B. | |
| 53. |
Gaseous diffusivity at atmospheric pressure is of the order of __________ cm 2 /second. |
| A. | 1 |
| B. | 1 to 5 |
| C. | 5 to 10 |
| D. | > 10 |
| Answer» B. 1 to 5 | |
| 54. |
Humid volume is the total volume in m 3 of 1 kg of |
| A. | vapour laden gas at 1 atm. and room temperature. |
| B. | gas plus its accompanying vapour at 1 atm. and room temperature. |
| C. | gas plus its accompanying vapour at 1 atm. and gas temperature. |
| D. | vapour laden gas at 1 atm. and gas temperature. |
| Answer» D. vapour laden gas at 1 atm. and gas temperature. | |
| 55. |
The diffusivity, D AB (for component A diffusing in B ) is equal to the diffusivity D BA (for component B diffusing in A ) for a binary mixture of |
| A. | Newtonion liquids |
| B. | non-Newtonion liquids |
| C. | ideal gases |
| D. | real gases |
| Answer» D. real gases | |
| 56. |
Mass transfer co-efficient is directly proportional to D AB 0.5 , according to __________ theory. |
| A. | penetration |
| B. | surface renewal |
| C. | film |
| D. | none of these |
| Answer» B. surface renewal | |
| 57. |
The diffusion co-efficient in m 2 /s. of acetic acid in benzene (liquid in liquid) is |
| A. | 2.09 x 10 -4 |
| B. | 2.09 x 10 -5 |
| C. | 2.09 x 10 -9 |
| D. | 2.09 x 10 -12 |
| Answer» D. 2.09 x 10 -12 | |
| 58. |
The equation, is for |
| A. | steady state equimolar counter diffusion |
| B. | Fick's first law of diffusion |
| C. | steady state diffusion for stagnant case |
| D. | liquid M.T.C. by penetration theory. |
| Answer» B. Fick's first law of diffusion | |
| 59. |
Molecular seives are regenerated by heating to __________ °C. |
| A. | < 150 |
| B. | 200-330 |
| C. | > 500 |
| D. | > 1000 |
| Answer» C. > 500 | |
| 60. |
The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, K c & K m are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, K p = M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.) |
| A. | K c = K p = K m |
| B. | K c = K p / RT = K m . RT / P |
| C. | K c = K p . RT = K m . RT / p |
| D. | none of these |
| Answer» D. none of these | |
| 61. |
The value of N A /( N A + N B ) for steady state molecular diffusion of gas ' A ' through non-diffusing gas ' B ' is |
| A. | 1 |
| B. | ? |
| C. | 0.5 |
| D. | 2 |
| Answer» B. ? | |
| 62. |
In gas-liquid contact operation, the number of ideal stages, . This is true when the stripping factor ' S ' is |
| A. | S > 1 |
| B. | S < 1 |
| C. | S = 1 |
| D. | S = ? |
| Answer» B. S < 1 | |
| 63. |
When acetone is added in a two layer mixture of methyl isobutyl ketone and water at 30°C, the acetone distributes between the two layers and the composition of the layer follows two solubility curves. For this system, |
| A. | as the acetone concentration increases, the solubility curves approach each other. |
| B. | both the phases become identical at a particular common point on both the solubility curves called the plait point. |
| C. | the distribution curve which is a plot between x (acetone concentration in one phase) and y (acetone concentration in other phase) is analogous to x-y curve used in distillation and absorption terminates on the x = y diagonal at the concentration of the plait point. |
| D. | all (a), (b) and (c). |
| Answer» E. | |
| 64. |
Prandtl number for water at 20°C is about |
| A. | 7 |
| B. | 70 |
| C. | 0.7 |
| D. | 150. |
| Answer» B. 70 | |
| 65. |
With increase in gas rate, the number of transfer units, N toG , for a fixed degree of absorption by a fixed amount of solvent |
| A. | increases |
| B. | decreases |
| C. | decreases linearly |
| D. | remains unaffected |
| Answer» B. decreases | |
| 66. |
Weight of 1 m 3 of humid air as compared to 1 m 3 of dry air, under the same conditions, is |
| A. | less |
| B. | more |
| C. | same |
| D. | unpredictable |
| Answer» B. more | |
| 67. |
For the case of flow of air past a wet bulb thermometer (air water vapour system), the approximate value of h 2 / k y . C z is around |
| A. | 0.60 |
| B. | 0.24 |
| C. | 1 |
| D. | 0.72 |
| Answer» D. 0.72 | |
| 68. |
At equilibrium the concentration of water in vapour phase (C * )in kg/m 3 of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C * = 0.0667m. To maintain dry conditions in a room of air space 100m 3 containing 2.2 kg of water vapour initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is |
| A. | 0.0 |
| B. | 0.2 |
| C. | 0.4 |
| D. | 1.0 |
| Answer» D. 1.0 | |
| 69. |
Liquid diffusivity is of the order of __________ cm 2 /second. |
| A. | 0.01 |
| B. | 0.1 |
| C. | 10 -5 to 10 -6 |
| D. | > 1 |
| Answer» D. > 1 | |
| 70. |
Absorption with chemical reaction' is involved in the removal of |
| A. | carbon dioxide from gaseous stream using alkaline solution. |
| B. | benzol from coke oven gas using solar oil/wash oil. |
| C. | ammonia from coke oven gas using refrigerated water. |
| D. | tar from coke oven gas in primary gas coolers using chilled water. |
| Answer» B. benzol from coke oven gas using solar oil/wash oil. | |
| 71. |
Deairation (removal of O 2 ) of water is done by |
| A. | rectification |
| B. | absorption |
| C. | ion-exchange |
| D. | adsorption |
| Answer» D. adsorption | |
| 72. |
( N Re . N Sc ) is termed in mass transfer operation as the __________ number. |
| A. | Stanton |
| B. | Sherwood |
| C. | Peclet |
| D. | none of these |
| Answer» D. none of these | |
| 73. |
If the specific heats of a gas and a vapor are 0.2KJ/Kg.°K and 1.5 KJ/Kg.°K respectively, and the humidity is 0.01; the humid heat in KJ/°Kg. is |
| A. | 0.31 |
| B. | 0.107 |
| C. | 0.017 |
| D. | 0.215 |
| Answer» E. | |
| 74. |
Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m 2 and the solvent flow, rate is 400 moles of S/m 2 . hr. The equilibrium data is represented by Y = 3X 2 , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is |
| A. | 25% |
| B. | 50% |
| C. | 70% |
| D. | 90% |
| Answer» C. 70% | |
| 75. |
Mass transfer co-efficient ( K ) and diffusivity ( D ) are related according to film theory as |
| A. | K ? D |
| B. | K ? D |
| C. | K ? D 1.5 |
| D. | K ? D 2 |
| Answer» D. K ? D 2 | |
| 76. |
Absorption factor is defined as (where, S 1 = slope of the operating line S 2 = slope of the equilibrium curve) |
| A. | S 2 / S 1 |
| B. | S 1 / S 2 |
| C. | S 1 - S 2 |
| D. | S 1 x S 2 |
| Answer» C. S 1 - S 2 | |
| 77. |
In a packed absorption tower, if the equilibrium and operating lines are both straight lines, then the ratio, HETP/HTU OG __________ the absorption factor. |
| A. | increases with increase in |
| B. | is one at unity value of |
| C. | both (a) and (b) |
| D. | neither (a) nor (b) |
| Answer» D. neither (a) nor (b) | |
| 78. |
The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, N Pr = N Sc = __________ |
| A. | 1 |
| B. | 0.5 |
| C. | 10 |
| D. | 0 |
| Answer» B. 0.5 | |
| 79. |
Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapour by 1°F is called the |
| A. | latent heat |
| B. | humid heat |
| C. | specific heat |
| D. | sensible heat |
| Answer» D. sensible heat | |
| 80. |
Air initially at 101. 3 kPa and 40°C and with a relative humidity of 50%, is cooled at constant pressure to 30°C. The cooled air has a |
| A. | higher dew point. |
| B. | higher absolute (specific) humidity. |
| C. | higher relative humidity |
| D. | higher wet bulb temperature. |
| Answer» D. higher wet bulb temperature. | |