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MT Test #6
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Question 1 of 20
1. Question
1 pointsCategory: MASS TRANSFERMinimum reflux ratio in a distillation column results in
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Optimum number of trays
Minimum reboiler size
Maximum condenser size
Minimum number of trays 
Question 2 of 20
2. Question
1 pointsCategory: MASS TRANSFERThe feed to a binary distillation column has 40 mol% vapor and 60 mol% liquid. Then, the slop of the qline in the McCabeThiele plot is
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Question 3 of 20
3. Question
1 pointsCategory: MODERATEIn a binary mixture containing components A and B, the relative volatility of A with respect to B is 2.5 when mole fractions are used. The molecular weights of A and B are 78 and 92 respectively. If the compositions are, however, expressed in mass fractions, then the relative volatility will be
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Question 4 of 20
4. Question
1 pointsCategory: MODERATEThe equilibrium data of component A in the two phases B and C are given below.
The estimate of Y for x = 4 by fitting a quadratic expression of a form Y = mx^{2} for the above data is
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Question 5 of 20
5. Question
1 pointsCategory: MODERATEH_{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 given by Y = 1.5x. 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 metre) corresponding to an operating line given by y = 5x + 0.001 is
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Question 6 of 20
6. Question
1 pointsCategory: DIFFICULTA thin liquid film flows at steady state along a vertical surface as shown in the figure. The average velocity of the liquid film is 0.05 m/s. The viscosity of the liquid is 1 CP and its density is 1000 kg/m^{3}. The initially pure liquid absorbs a sparingly soluble gas from air as it flows down. The length of the wall is 2 m and its width is 0.5 m. The solubility of the gas in the liquid is 3.4 x10^{2} kmol/m^{3} and isothermal conditions may be assumed.
If the exit average concentration in the liquid is measured to be 1.4 x10^{2} kmol/m^{3}, the total mass transfer rate (in kmol/s) of the sparingly soluble gas into the liquid is
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Question 7 of 20
7. Question
1 pointsCategory: HEAT TRANSFERMatch the following dimensionless numbers with the appropriate ratio of forces.
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Question 8 of 20
8. Question
1 pointsCategory: EASYIn a tray column, separating a binary mixture, with nonideal stages, which one of the following statements is true?
Correct
In a tray column, separating a binary mixture, with nonideal stages , Murphree efficiency can exceed 100 %.
Incorrect
In a tray column, separating a binary mixture, with nonideal stages , Murphree efficiency can exceed 100 %.

Question 9 of 20
9. Question
1 pointsCategory: MASS TRANSFERGiven the following statements listed from (P) to (T), select the correct combination of true statements from the choices that follow this list.
(P) Plate columns are preferred when the operation involves liquids containing suspended solids
(Q) Packed towers are preferred if the liquids have a large foaming tendency.
(R) The pressure drop through packed towers is more than the pressure drop through plate columns designed for the same duty.
(S) Packed columns are preferred when large temperature changes are involved in distillation operations.
(T) Packed towers are cheaper than plate towers if highly corrosive fluids are handled.
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Question 10 of 20
10. Question
1 pointsThe wet bulb temperature Tw for the above mixture would be
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Question 11 of 20
11. Question
1 pointsCategory: DIFFICULTAt 25^{0}C and 90% relative humidity, water evaporates from the surface of a lake at the rate of 1.0 kg/m^{2}/h. The relative humidity that will lead to an evaporation rate of 3.0 kg/m^{2}/h, with other conditions remaining the same, is
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Question 12 of 20
12. Question
1 pointsCategory: MODERATEA binary feed mixture containing equimolar quantities of components S and T is to be distilled in a fractionating tower at atmospheric pressure. The distillate contains 96 mol% S. The qline (feed line) intersects the equilibrium line at x ‘ = 0.46 and y ‘ = 0.66, where x ‘ and y ‘ are mole fractions. Assume that the McCabeThiele method is applicable and the relative volatility is constant.
The minimum reflux ratio is
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Question 13 of 20
13. Question
1 pointsCategory: MODERATEThe mole fraction of methanol in the Feed is 0.5, and the feed flow rate is 1000 kmol/h. The feed is preheated in a heater with heat duty Q_{h} and is subsequently flashed in the drum. The flash drum can be assumed to be an equilibrium stage, operating adiabatically. The equilibrium relation between the mole fractions of methanol in the vapor and liquid phases is y* = 4x. The ratio of distillate to feed flow rate is 0.5.
The mole fraction of methanol in the distillate is
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Question 14 of 20
14. Question
1 pointsCategory: MODERATEA flash distillation drum (see figure below) is used to separate a methanolwater mixture. The mole fraction of methanol in the Feed is 0.5, and the feed flow rate is 1000 kmol/h. The feed is preheated in a heater with heat duty Q_{h} and is subsequently flashed in the drum. The flash drum can be assumed to be an equilibrium stage, operating adiabatically. The equilibrium relation between the mole fractions of methanol in the vapor and liquid phases is y* = 4x. The ratio of distillate to feed flow rate is 0.5.
If the enthalpy of the distillate with reference to the feed is 3000 kJ/kmol, and the enthalpy of the bottom with reference to the feed is 1000 kJ/kmol, the heat duty of the preheater (Q_{h} in kJ/h) is
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Question 15 of 20
15. Question
1 pointsCategory: MODERATEA feed (F) containing a soIut1s contacted with a solvent (S) in an ideal stage as shown in the figure below. Only the solute transfers into the solvent. The flow rates of all the streams are shown on a solute free basis and indicated by the subscript S. The compositions of the streams are expressed on a mole ratio basis The extract leaving the contactor is divided into two equal parts, one part collected s the pio4utt (P) and the other stream is recycled to join the solvent. The equilibrium relationship is Y* = 2X.
The product flow rate (PS) and composition are :
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Question 16 of 20
16. Question
1 pointsCategory: MODERATETwo solid discs of benzoic acid (molecular weight = 122) of equal dimensions are spinning separately in large volumes of water and air at 300 K. The mass transfer coefficients for benzoic acid in water and air are 0.9 x10^{5 }and 0.47×10^{2 }m/s respectively. The solubility of benzoic acid in water is 3 kg/m^{3} and the equilibrium vapor pressure of benzoic acid in air is 0.04 kPa. Then the disc
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Question 17 of 20
17. Question
1 pointsCategory: EASYAn ideal flash vaporization is carried out with a binary mixture at constant temperature and pressure. A process upset leads to an increase in the mole fraction of the heavy component in the feed. The flash vessel continuous to operate at the previous temperature and pressure and still produces liquid and vapor. After the steady state is reestablished.
Correct
After steady state is reestablished , the new equilibrium compositions of the vapour and liquid products will remain as they were before the upset occurred .
Incorrect
After steady state is reestablished , the new equilibrium compositions of the vapour and liquid products will remain as they were before the upset occurred .

Question 18 of 20
18. Question
1 pointsCategory: MODERATEA batch distillation operation is carried out to separate a feed containing 100 moles of a binary mixture of A and B. The mole fraction of A in the feed is 0.7. The distillation progresses until the mole fraction of A in the residue decreases to 0.6. The equilibrium curve in this composition range may be linearized to y* = 0.7353x + 0.3088. Here, x and y are the mole fractions of the more volatile component A in the liquid and vapor phases respectively. The number of moles of residue is
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Question 19 of 20
19. Question
1 pointsCategory: MODERATEFor a system containing species P, Q, and R, the composition at point k on the ternary plot is
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Question 20 of 20
20. Question
1 pointsCategory: MODERATEA binary feed mixture containing equimolar quantities of components S and T is to be distilled in a fractionating tower at atmospheric pressure. The distillate contains 96 mol% S. The qline (feed line) intersects the equilibrium line at x ‘ = 0.46 and y ‘ = 0.66, where x ‘ and y ‘ are mole fractions. Assume that the McCabeThiele method is applicable and the relative volatility is constant.
The feed is
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