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.
| 1. |
The McCabe ? L law states that the |
| A. | linear crystal growth rate depends on the degree of supersaturation. |
| B. | molar heats of vaporisation of components are nearly equal. |
| C. | linear crystal growth rate depends on the crystal size. |
| D. | linear crystal growth rate does not depend on the crystal size. |
| Answer» C. linear crystal growth rate depends on the crystal size. | |
| 2. |
Penetration theory states that the mass transfer co-coefficient is equal to (where, D e is diffusivity and ' t ' is time) |
| A. | ( D e .t ) 1/2 |
| B. | ( D e /t ) 1/2 |
| C. | (4 D e /? t ) 1/2 |
| D. | (4 D e / t ) |
| Answer» D. (4 D e / t ) | |
| 3. |
In a single stage extraction process, 10 kg of pure solvent S (containing no solute A) is mixed with 30 kg of feed F containing A at a mass fraction x f = 0.2. The mixture splits into an extract phase E and a raf-finate phase R containing A at x B = 0.5 and x R = 0.05 respectively. The total mass of the extract phase is (in Kg) |
| A. | 6.89 |
| B. | 8.89 |
| C. | 10 |
| D. | 8.25 |
| Answer» C. 10 | |
| 4. |
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» C. 1 | |
| 5. |
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» D. K ? D 2 | |
| 6. |
Unsaturated air (with dry and wet bulb temperatures being 35 and 25°C respectively) is passed through water spray chamber maintained at 35°C. The air will be |
| A. | cooled |
| B. | humidified |
| C. | both (a) & (b) |
| D. | dehumidified |
| Answer» C. both (a) & (b) | |
| 7. |
A solid is being dried in the linear drying rate regime from moisture content X o to X F . The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture X o . The drying time for M = ( L s / AR c ) is (where, L = total mass of dry solid, A = total surface area for drying R c = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids)) |
| A. | M ( X o - X F ) |
| B. | M ( X o / X F ) |
| C. | M ln( X o / X F ) |
| D. | MX o ln( X o / X F ) |
| Answer» E. | |
| 8. |
According to Chilton-Colburn analogy for mass transfer, N St . N Sc 2/3 is equal to |
| A. | f |
| B. | f /2 |
| C. | 2 f |
| D. | 1/ f |
| Answer» C. 2 f | |
| 9. |
H 2 S present in naphtha reformed gas is removed by absorbing with |
| A. | ethanolamine |
| B. | K 2 CO 3 |
| C. | HCl |
| D. | vacuum gas oil |
| Answer» B. K 2 CO 3 | |
| 10. |
Mass transfer co-efficient ' K ' according to penetration theory varies with mass dif-fusivity as |
| A. | D 0.5 |
| B. | D |
| C. | 1/ D |
| D. | D 1.5 |
| Answer» B. D | |
| 11. |
Nitrobenzene (boiling point = 210.6°C) is steam distilled at 1 atm pressure.Nitrobenzene will distill off __________ °C. |
| A. | at < 100 |
| B. | at > 210.6 |
| C. | between 100 and 210 |
| D. | none of these |
| Answer» B. at > 210.6 | |
| 12. |
An air-water vapour mixture has a dry bulb temperature of 60°C and a dew point temperature of 40°C. The total pressure is 101.3 kPa and the vapour pressure of water at 40°C and 60°C are 7.30 kPa and 19.91 kPa respectively.The humidity of air sample expressed as kg of water vapour/kg of dry air is |
| A. | 0.048 |
| B. | 0.079 |
| C. | 0.122 |
| D. | 0.152 |
| Answer» E. | |
| 13. |
The value of N A /( N A + N B ), for steady state equimolal counter diffusion of two gases ' A ' and ' B ' is |
| A. | 1 |
| B. | ? |
| C. | 0.5 |
| D. | 2 |
| Answer» C. 0.5 | |
| 14. |
J D factor for mass transfer is a function of Reynolds number. Mass transfer by molecular diffusion from a single drop to surrounding still air is given by |
| A. | N sh = 2 |
| B. | N st = 2 |
| C. | N sc = 2 |
| D. | none of these |
| Answer» B. N st = 2 | |
| 15. |
In a distillation operation, what is the effect of the temperature of the reflux stream (given below) on the condenser and reboiler loads ? Reflux conditions: (i) Reflux stream is completely liquid and is at its bubble point. (ii) Reflux stream is below its bubble point. |
| A. | Condenser and reboiler loads are the same in both the cases. |
| B. | Reboiler load is the same in both the cases but condenser load is higher in case (ii). |
| C. | Condenser load is the same in both the cases but reboiler load is higher in case (ii). |
| D. | Both condensor and reboiler loads are higher in case (ii) as compared to case (i). |
| Answer» E. | |
| 16. |
The expression, ln( F / W ) = is |
| A. | differential distillation equation |
| B. | for N toG in absorption for dilute mixture |
| C. | slope of q -line in McCabe-Thiele method |
| D. | for relative volatility |
| Answer» B. for N toG in absorption for dilute mixture | |
| 17. |
Acetone is to be removed from air in an isothermal dilute absorber using pure water as solvent. The incoming air contains 5 mole% of acetone (y in = 0.05). The design equation to be used for obtaining the number of trays (N) of the absorber is, N+2 = 6 log (y in /y out ).For 98% recovery of acetone, the number of trays required is/are |
| A. | 1 |
| B. | 8 |
| C. | 9 |
| D. | 10 |
| Answer» D. 10 | |
| 18. |
Which of the following is a suitable absorbent for removal of H 2 S from natural gas ? |
| A. | Vetrocoke solution |
| B. | Monoethanol amine (MEA) |
| C. | Dilute |
| D. | Hot water |
| Answer» C. Dilute | |
| 19. |
CO 2 can be absorbed by |
| A. | hot cupric oxide |
| B. | heated charcoal |
| C. | cold Ca(OH) 2 |
| D. | alumina |
| Answer» C. cold Ca(OH) 2 | |
| 20. |
( N Sh / N Re . N Sc ) is termed in mass transfer operation as the |
| A. | Stanton number |
| B. | Peclet number |
| C. | thermal diffusivity |
| D. | momentum diffusivity |
| Answer» B. Peclet number | |
| 21. |
L / mG is the expression for |
| A. | absorption factor |
| B. | Brinkman number |
| C. | slope of operating line in absorber |
| D. | slope of operating line in stripper. |
| Answer» B. Brinkman number | |
| 22. |
A mixture of 10% C 6 H 6 vapour in air at 25°C and 750 mm Hg has a dew point of 20°C. Its dew point at 30°C and 700 mm Hg will be around __________ °C. |
| A. | 21.7 |
| B. | 20 |
| C. | 27.3 |
| D. | 18.7 |
| Answer» E. | |
| 23. |
1 kg of a saturated aqueous solution of a highly soluble component A at 60°C is cooled to 25°C. The solubility limits of A are (0.6 kgA/kg water) at 60°C and (0.2 kgA/kg water) at 25°C. The amount in kg of the crystals formed is |
| A. | 0.4 |
| B. | 0.25 |
| C. | 0.2 |
| D. | 0.175 |
| Answer» D. 0.175 | |
| 24. |
ADDUCTS' and 'CLATHRATES' are used in case of |
| A. | extractive distillation. |
| B. | crystallisation. |
| C. | absorption. |
| D. | none of these. |
| Answer» C. absorption. | |
| 25. |
N Sc / N Pr is called the |
| A. | psychrometric ratio |
| B. | Lewis number |
| C. | Sherwood number |
| D. | Stantan number |
| Answer» C. Sherwood number | |
| 26. |
Component A is diffusing in a medium B . The flux N A relative to a stationary point is equal to the flux due to molecular difusion, if |
| A. | mass transfer is accompanied by reaction. |
| B. | diffusion of A is in stagnant medium B . |
| C. | molecular mean free path is high. |
| D. | there is equimolar counter diffusion. |
| Answer» E. | |
| 27. |
Unsaturated air (with dry bulb temperature and dew point being 35°C and 18°C respectively) is passed through a water spray chamber maintained at 15°C. The air will be cooled |
| A. | and humidified. |
| B. | and dehumidified with increase in wet bulb temperature. |
| C. | at the same relative humidity. |
| D. | and dehumidified with decrease in wet bulb temperature. |
| Answer» E. | |
| 28. |
The rough value of diffusion co-efficient of water vapor into air at 25°C may be about __________ cm 2 /sec. |
| A. | 0.25 |
| B. | 2.5 |
| C. | 1.25 |
| D. | 0.0025 |
| Answer» B. 2.5 | |
| 29. |
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 ( K c ) for the same sytem is |
| A. | 100 |
| B. | 10 |
| C. | 5 |
| D. | 1 |
| Answer» C. 5 | |
| 30. |
Rayleigh's equation applies to __________ distillation. |
| A. | continuous |
| B. | steam |
| C. | differential |
| D. | flash |
| Answer» D. flash | |
| 31. |
Mass transfer co-efficient is directly proportional to D AB according to the __________ theory. |
| A. | film |
| B. | penetration |
| C. | surface-renewal |
| D. | none of these |
| Answer» B. penetration | |
| 32. |
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» D. Evaporative cooling | |
| 33. |
H 2 S is being absorbed in a gas absorber unit. The height of the transfer unit based on the overall mass transfer coefficient on the gas side is 0.4 m. The equilibrium data is given by, y = 1.5 x. The bulk concentration of H 2 S has to be reduced from 0.05 to 0.001 mole fraction in the gas side. The height of the tower (in metres) corresponding to an operating line given by, y = 5x + 0.001 is |
| A. | 2.0 |
| B. | 1.56 |
| C. | 1.0 |
| D. | 0.56 |
| Answer» B. 1.56 | |
| 34. |
According to Poiseuille's law, the permeability for gas flow through a capillary is proportional to (where, ? = gas viscosity) |
| A. | ? |
| B. | 1/? |
| C. | ? |
| D. | ? 2 |
| Answer» C. ? | |
| 35. |
The wet and 'dry bulb temperature for a vapour-gas mixture are 25°C and 30°C respectively. If the mixture is heated to 45°C at constant pressure, the wet bulb temperature will be __________ °C. |
| A. | 25 |
| B. | > 25 |
| C. | < 25 |
| D. | - 25 |
| Answer» C. < 25 | |
| 36. |
In a packed tower, the value of HETP equals HTU OG , when the equilibrium and the operating lines are (where, HETP = height equivalant to a theoretical plate HTU OG = overall gas phase height of a transfer unit) |
| A. | straight |
| B. | parallel |
| C. | both (a) & (b) |
| D. | neither (a) nor (b) |
| Answer» D. neither (a) nor (b) | |
| 37. |
With increase in solvent rate, the number of transfer units, N toG , for a fixed degree of absorption from a fixed amount of gas |
| A. | increases |
| B. | decreases |
| C. | decreases linearly |
| D. | remains unaffected |
| Answer» C. decreases linearly | |
| 38. |
If a 1 and a 2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement. |
| A. | a 1 = a 2 |
| B. | a 1 = 2 a 2 |
| C. | a 1 = 0.5 a 2 |
| D. | none of these |
| Answer» E. | |
| 39. |
The diffusivity ( D ) in a binary gas mixture is related to the temperature ( T ) as |
| A. | D ? T |
| B. | D ? T 0.5 |
| C. | D ? T 1.5 |
| D. | D ? T 2 |
| Answer» D. D ? T 2 | |
| 40. |
The overall mass transfer co-efficient for the absorption of SO 2 in air with dilute NaOH solution can be increased substantially by |
| A. | increasing the gas film co-efficient. |
| B. | increasing the liquid film co-efficient. |
| C. | increasing the total pressure. |
| D. | decreasing the total pressure. |
| Answer» B. increasing the liquid film co-efficient. | |
| 41. |
The value of L / mG ratio for economical absorption operation ranges from |
| A. | 0.5 to 0.8 |
| B. | 0.8 to 1.2 |
| C. | 1.25 to 2.0 |
| D. | 2.5 to 3.5 |
| Answer» D. 2.5 to 3.5 | |
| 42. |
Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 x 10 -3 kg mole/m 2 .s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m 2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.01 respectively is |
| A. | 5.6 x 10 -4 |
| B. | 8.5 x 10 -4 |
| C. | 5.6 x 10 -3 |
| D. | 8.5 x 10 -3 |
| Answer» C. 5.6 x 10 -3 | |
| 43. |
The interfacial area per unit volume of dispersion, in a gas-liquid contactor, for fractional hold up of gas = 0.1 and gas bubble diameter = 0.5 mm is given by (in m 2 /m 3 ) |
| A. | 500 |
| B. | 1200 |
| C. | 900 |
| D. | 800 |
| Answer» B. 1200 | |
| 44. |
Pick out the correct relationship. (where, R i = internal reflux ratio R o = external reflux ratio. ) |
| A. | (1 + R o ) = R o / R i |
| B. | (1 - R o ) = R o / R i |
| C. | (1 + R i ) = R o / R i |
| D. | (1 - R i ) = R o / R i |
| Answer» B. (1 - R o ) = R o / R i | |
| 45. |
According to the Fenske equation, what will be the minimum number of plates required in a distillation column to separate an equimolar binary mixture of components A and B into an overhead fraction containing 99 mol% A and a bottom fraction containing 98 mol% B ? Assume that relative volatility (? AB = 2) does not change appreciably in the coloumn. |
| A. | 5 |
| B. | 9 |
| C. | 12 |
| D. | 28 |
| Answer» D. 28 | |
| 46. |
The individual mass transfer co-efficients (moles/m 2 . s) for absorption of a solute from a gas mixture into a liquid solvent are, K L = 4.5 and K G = 1.5. The slope of the equilibrium line is 3. Which of the following resistance (s) is (are) controlling ? |
| A. | liquid side |
| B. | gas side |
| C. | interfacial |
| D. | both liquid and gas side |
| Answer» C. interfacial | |
| 47. |
Unsaturated air (with dry bulb and wet bulb temperatures being 45°C and 25°C respectively) is passed through a water spray chamber maintained at 23°C. The air will be cooled and |
| A. | humidified with wet bulb temperature decreasing. |
| B. | humidified at constant wet bulb temperature. |
| C. | dehumidified. |
| D. | none of these |
| Answer» B. humidified at constant wet bulb temperature. | |
| 48. |
A distillation column separates 10000 kg/hr of a benzene-toluene mixture as shown in the figure below : In the figure x F , x D and x W represent the weight fraction of benzene in the feed, distillate and residue respectively. The reflux ratio is |
| A. | 0.5 |
| B. | 0.6 |
| C. | 1.0 |
| D. | 2.0 |
| Answer» C. 1.0 | |
| 49. |
Mass transfer co-efficient varies as D AB 0.5 , according to the __________ theory. |
| A. | film |
| B. | surface renewal |
| C. | penetration |
| D. | none of these |
| Answer» C. penetration | |
| 50. |
If R m is the minimum reflux ratio, the optimum reflux ratio may be around __________ R m . |
| A. | 1.2 to 1.5 |
| B. | 2.5 to 3 |
| C. | 3 to 4 |
| D. | 5 |
| Answer» B. 2.5 to 3 | |