McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 51. |
Which of the following processes is followed by unsaturated air (with dry bulb temperature 12°C and relative humidity 47%) passing through water spray washer (temperature of water being constant at 40°C? |
| A. | Humidification only |
| B. | Heating only |
| C. | Both heating and humidification |
| D. | Evaporative cooling |
| Answer» C. Both heating and humidification | |
| 52. |
The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if |
| A. | NSc = 1 |
| B. | NSc = NPr = NLe |
| C. | NPr = NLe |
| D. | NSc = NLe |
| Answer» B. NSc = NPr = NLe | |
| 53. |
Pick out the wrong statement. Generally for physical adsorption, a gas of |
| A. | Higher molecular weight is adsorbed in preference to a gas of low molecular weight |
| B. | High critical temperature is adsorbed in preference to a gas of low critical temperature |
| C. | Low volatility is adsorbed in preference to a gas of high volatility |
| D. | None of these |
| Answer» D. None of these | |
| 54. |
Co-current absorbers are usually used when the gas to be dissolved in the liquid is |
| A. | Sparingly soluble |
| B. | Highly soluble |
| C. | A pure substance |
| D. | A mixture |
| Answer» C. A pure substance | |
| 55. |
Molecular sieves are regenerated by heating to __________ °C. |
| A. | < 150 |
| B. | 200-330 |
| C. | > 500 |
| D. | > 1000 |
| Answer» B. 200-330 | |
| 56. |
In triangular co-ordinates, the ternary composition point falls __________ of the triangle. |
| A. | In the corners |
| B. | Inside |
| C. | On the sides |
| D. | None of these |
| Answer» B. Inside | |
| 57. |
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 iden 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» D. All (A), (B) and (C) | |
| 58. |
During sensible cooling process |
| A. | Relative humidity decreases |
| B. | Relative humidity increases |
| C. | Wet bulb temperature decreases |
| D. | Both (B) and (C) |
| Answer» D. Both (B) and (C) | |
| 59. |
For stripping of a gas in a counter current stripper, the operating line |
| A. | Lies above the equilibrium curve |
| B. | Lies below the equilibrium curve |
| C. | Can lie above or below the equilibrium curve |
| D. | Is always parallel to the equilibrium curve |
| Answer» C. Can lie above or below the equilibrium curve | |
| 60. |
The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc) for the same system is. |
| A. | 100 |
| B. | 10 |
| C. | 5 |
| D. | 1 |
| Answer» B. 10 | |
| 61. |
The boiling points of pure components of a binary system __________ with increase in total pressure of the system. |
| A. | Decreases |
| B. | Increases |
| C. | Remains unchanged |
| D. | May increase or decrease, depends on the system |
| Answer» B. Increases | |
| 62. |
In gas-liquid contact operation, the number of ideal stages, N = (xa - xb)/(xb - x*b). This is true when the stripping factor 'S' is |
| A. | S > 1 |
| B. | S < 1 |
| C. | S = 1 |
| D. | S = ∞ |
| Answer» A. S > 1 | |
| 63. |
Large scale usage of flash distillation is practised in |
| A. | Soap manufacturing |
| B. | Ammonia synthesis plant |
| C. | Polymerisation industry |
| D. | Petroleum refining |
| Answer» D. Petroleum refining | |
| 64. |
Drying of a solid involves __________ transfer. |
| A. | Only heat |
| B. | Only mass |
| C. | Both heat and mass |
| D. | None of these |
| Answer» C. Both heat and mass | |
| 65. |
Desulphurisation of petrol is done in a |
| A. | Bollman extractor |
| B. | Rotating disc extractor |
| C. | Packed extraction column |
| D. | Plate type extraction column |
| Answer» B. Rotating disc extractor | |
| 66. |
Pick out the wrong statement |
| A. | Co-current absorbers are usually used, when the gas to be dissolved in the liquid is a pure substance |
| B. | In case of gas absorption, HETP is equal to HTU, when both the operating line & the equilibrium lines are parallel |
| C. | Hatta number is important in case of gas absorption with chemical reaction |
| D. | In actual practice, absorption is an endothermic process, while stripping is an exothermic process |
| Answer» D. In actual practice, absorption is an endothermic process, while stripping is an exothermic process | |
| 67. |
Which of the following increases during evaporative cooling process with recirculated water supply? |
| A. | Wet bulb temperature |
| B. | Relative humidity |
| C. | Partial pressure of vapour |
| D. | Both (B) and (C) |
| Answer» D. Both (B) and (C) | |
| 68. |
Operating velocity in a packed tower is usually __________ the flooding velocity. |
| A. | Half |
| B. | Twice |
| C. | Equal to |
| D. | More than |
| Answer» A. Half | |
| 69. |
For gas absorption, low viscosity solvents are preferred, because of their |
| A. | Better flow characteristics |
| B. | Low pumping pressure drop |
| C. | Rapid absorption rates |
| D. | All (A), (B) and (C) |
| Answer» D. All (A), (B) and (C) | |
| 70. |
Which of the following is used for the concentration of rubber latex? |
| A. | Agitated film evaporator |
| B. | Long tube vertical evaporator |
| C. | Short tube evaporator |
| D. | Calandria |
| Answer» A. Agitated film evaporator | |
| 71. |
Pressure drop through plate tower as compared to that through packed tower, for the same duty will be |
| A. | Less |
| B. | More |
| C. | Equal |
| D. | Either (A) or (B); depends on the packing height |
| Answer» B. More | |
| 72. |
In case of absorption & stripping, the interface of the liquid & gas phases are present in equilibrium, when the diffusional resistance of __________ is zero. |
| A. | Interface |
| B. | Gas phase |
| C. | Liquid phase |
| D. | All 'a', 'b' & 'c' |
| Answer» A. Interface | |
| 73. |
Henry's law states that the |
| A. | Partial pressure of a component over a solution is proportional to its mole fraction in the liquid |
| B. | Partial pressure of a component over a solution is proportional to the mole fraction in the vapour |
| C. | Vapour pressure is equal to the product of the mole fraction and total pressure |
| D. | Partial pressure is equal to the product of the mole fraction and total pressure |
| Answer» A. Partial pressure of a component over a solution is proportional to its mole fraction in the liquid | |
| 74. |
The change in enthalpy, when a unit quantity of gas is absorbed by relatively large quantity of adsorbent (on which a definite concentration of the adsorbed gas already exists) is termed as the |
| A. | Differential heat of adsorption |
| B. | Heat of wetting |
| C. | Integral heat of adsorption |
| D. | None of these |
| Answer» A. Differential heat of adsorption | |
| 75. |
A 25 cm × 25 cm × 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m × 1m × 1cm flat sheet of the same material is to be dried from one side only. Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is |
| A. | 1000 |
| B. | 1500 |
| C. | 2000 |
| D. | 2500 |
| Answer» A. 1000 | |
| 76. |
Moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the __________ moisture. |
| A. | Unbound |
| B. | Critical |
| C. | Free |
| D. | Bound |
| Answer» A. Unbound | |
| 77. |
Swenson-Walker crystalliser is a __________ unit. |
| A. | Continuous |
| B. | Batch |
| C. | Semi-batch |
| D. | Cooling (adiabatic)-cum-evaporation |
| Answer» A. Continuous | |
| 78. |
For a binary mixture distillation process, the degree of freedom is 2. However, if the pressure is fixed in this process, the number of independent variables in this process will be |
| A. | 1 |
| B. | 0 |
| C. | 2 |
| D. | 3 |
| Answer» A. 1 | |
| 79. |
Calculation of mass transfer co-efficient is mostly/normally done using __________ theory. |
| A. | Surface renewal |
| B. | Film |
| C. | Penetration |
| D. | None of these |
| Answer» B. Film | |
| 80. |
With increase in temperature, the leaching rate increases because of the |
| A. | Increased diffusivity |
| B. | Decreased viscosity of liquid |
| C. | Both (A) and (B) |
| D. | Neither (A) nor (B) |
| Answer» C. Both (A) and (B) | |
| 81. |
Relative volatility varies with the concentration of component for an ideal solution. The relative volatility of a binary mixture may be defined as the ratio of vapor pressure of component 'A' to that of component 'B', when |
| A. | Only vapor phase follows Raoult's law |
| B. | Only liquid phase obeys Dalton's law |
| C. | Liquid phase obeys Dalton's law and vapor phase obeys Raoult's law |
| D. | Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law |
| Answer» D. Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law | |
| 82. |
Which one of the following devices is not used for both the absorption as well as the liquidliquid extraction processes? |
| A. | Packed towers |
| B. | Plate towers |
| C. | Spray towers |
| D. | Wetted wall columns |
| Answer» D. Wetted wall columns | |
| 83. |
Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as |
| A. | K ∝D |
| B. | K ∝√D |
| C. | K ∝D 1.5 |
| D. | K ∝D 2 |
| Answer» B. K ∝√D | |
| 84. |
Pick out the wrong statement. |
| A. | Mechanical agitation is required, if the system has low interfacial tension |
| B. | Sieve tray towers are generally used for systems having low interfacial tension |
| C. | When Henry's law constant is very small, then the mass transfer rate is controlled by the gas film resistance |
| D. | Taylor-Prandtl analogy for heat and mass tr |
| Answer» C. When Henry's law constant is very small, then the mass transfer rate is controlled by the gas film resistance | |
| 85. |
For water-ethanol system, the minimum reflux ratio |
| A. | Is computed from the slope of the upper operating line that is tangent to the equilibrium curve |
| B. | Is computed from the intercept of the operating line |
| C. | Cannot be computed |
| D. | Is the optimum reflux ratio |
| Answer» A. Is computed from the slope of the upper operating line that is tangent to the equilibrium curve | |
| 86. |
Polar organic compounds are normally used as separating agents for the azeotropic and extractive distillation. Which of the following is the most important factor to be considered for the choice of the separating agent for extractive distillation? |
| A. | Cost |
| B. | Availability |
| C. | Toxicity |
| D. | Selectivity |
| Answer» D. Selectivity | |
| 87. |
At 750°K and 1 atm, the approximate value of Schmidt number for air is |
| A. | 0.01 |
| B. | 0.1 |
| C. | 1 |
| D. | 10 |
| Answer» B. 0.1 | |
| 88. |
What is the degree of freedom of an absorption process in which only one component is transferred between phases? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» C. 3 | |
| 89. |
Rayleigh equation applies to __________ distillation. |
| A. | Differential |
| B. | Flash |
| C. | Equilibrium |
| D. | Molecular |
| Answer» A. Differential | |
| 90. |
In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL) as |
| A. | KG = 1/KG + m/KL |
| B. | 1/KG = 1/KG + m/KL |
| C. | 1/KG = 1/KL + m/KG |
| D. | KG = 1/KL + m/KG |
| Answer» B. 1/KG = 1/KG + m/KL | |
| 91. |
Leaching of coarse solid lumps is also termed as |
| A. | Decoction |
| B. | Dissolution |
| C. | Percolation |
| D. | Agitation and settling |
| Answer» C. Percolation | |
| 92. |
Which of the following can be calculated theoretically using steam table and Dalton's law of partial pressure; if the relative humidity and dry bulb temperature of moist air is known? |
| A. | Dew point |
| B. | Humidity ratio |
| C. | Wet bulb temperature |
| D. | None of these |
| Answer» C. Wet bulb temperature | |
| 93. |
Danckwerts developed the __________ theory. |
| A. | Penetration |
| B. | Surface renewal |
| C. | Film |
| D. | None of these |
| Answer» B. Surface renewal | |
| 94. |
Steam distillation is used to |
| A. | Reduce the number of plates |
| B. | Avoid thermal decomposition of a component |
| C. | Increase the efficiency of separation |
| D. | Increase the total pressure of distillation |
| Answer» B. Avoid thermal decomposition of a component | |
| 95. |
When an unsaturated air-water mixture is heated at constant pressure, then |
| A. | The partial pressure of water vapour increases |
| B. | The specific humidity decreases |
| C. | The relative humidity increases |
| D. | The relative humidity decreases |
| Answer» D. The relative humidity decreases | |
| 96. |
Flash distillation is |
| A. | Same as differential distillation |
| B. | Used for multi-component systems like crude refining |
| C. | Same as simple distillation |
| D. | Most useful for handling binary systems |
| Answer» B. Used for multi-component systems like crude refining | |
| 97. |
Mechanism of moisture removal in case of freeze drying of food stuff is by |
| A. | Evaporation |
| B. | Sublimation |
| C. | Dehydration |
| D. | Adsorption |
| Answer» B. Sublimation | |
| 98. |
Molality is defined as the number of gm moles of solute per __________ of solvent. |
| A. | Litre |
| B. | gm |
| C. | Kg |
| D. | m3 |
| Answer» C. Kg | |
| 99. |
When the mixture to be distilled has a very high boiling point and the product material is heat sensitive, the separation technique to be used is __________ distillation. |
| A. | Continuous |
| B. | Steam |
| C. | Azeotropic |
| D. | None of these |
| Answer» B. Steam | |
| 100. |
Alcohol is dehydrated using __________ distillation. |
| A. | Extractive |
| B. | Azeotropic |
| C. | Steam |
| D. | Molecular |
| Answer» B. Azeotropic | |
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