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This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on Mass Transfer Set 12
Q1 | In a distillation column, with increase in the reflux ratio, the heat removed in the cooler
- Increases
- Decreases
- Remains unaffected
- And the heat required in reboiler decreases
Q2 | The feed to fractionating column is changed from saturated vapour to saturated liquid. If the separation and reflux ratio remains unchanged, the number of ideal stages will
- Increase
- Decrease
- Remain same
- Depend on saturated boiling point; may increase or decrease
Q3 | During constant rate drying period, vaporisation rate per unit drying surface area
- Decreases with time
- Increases with time
- Does not change with time
- Does not affect the moisture content of the wet solid
Q4 | A coalescer in a mixer-settler liquid-liquid extraction column
- Comprises of thin bed of substances of extended surface having high porosity
- Helps in increasing the bubble size entering the settler
- Helps in increasing the settling rate of the bubbles
- All 'a', 'b', & 'c'
Q5 | In which of the following unit operations, the selectivity is an important parameter?
- Distillation
- Solvent extraction
- Absorption
- None of these
Q6 | Flash distillation is suitable for separating the constituents of a binary system, which
- Form minimum boiling azeotrope
- Have very wide boiling points
- Have very close boiling points
- Form constant boiling azeotrope
Q7 | In case of an unsaturated mixture of gas and vapor, the percentage saturation is __________ its relative saturation.
- Lower than
- Higher than
- Equal to
- Either (A) or (B), depends on the mixture composition
Q8 | At __________ reflux, theoretical number of plates in a distillation coloumn is calculatedusing Fenske-Underwood equation.
- Operating
- Total
- Minimum
- Maximum permissible
Q9 | Pick out the correct statement.
- The slope of the stripping line is always less than unity
- For a given separation in a binary distillation column, with increase in reflux ratio (above the minimum reflux ratio), the fixed cost of the distillation column first increases and then decreases
- In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux
- Kremser-Brown-Souder's equation is used to calculate the efficiency of a plate tower
Q10 | In physical terms, Schmidt number means
- Thermal diffusivity/mass diffusivity
- Thermal diffusivity/momentum diffusivity
- Momentum diffusivity/mass diffusivity
- Mass diffusivity/thermal diffusivity
Q11 | Unit operation involved in the prilling of urea is
- Evaporation
- Drying
- Crystallisation
- Both (B) and (C)
Q12 | Degree of freedom for leaching and solvent extraction process is
- 0
- 1
- 2
- 3
Q13 | With increase in temperature, the solubility of gases in liquids, at fixed pressure
- Increases
- Decreases
- Remain same
- Either (A) or (B), depends on the system
Q14 | The equipment used in the extraction of highly corrosive radioactive liquids is
- Pulse column
- Spray column
- Mixer settler
- Baffle tower
Q15 | Tea percolation employs
- Liquid-liquid extraction
- Leaching
- Absorption
- None of these
Q16 | When the solvent dissolves very little of solute, then
- Solvent of low latent heat of vaporisation should be used
- Solvent of low freezing point should be used
- Large quantity of solvent is required to extract the solute
- Very small quantity of solvent is required
Q17 | Bollman extractor
- Is a static bed leaching equipment
- Is used for extraction of oil from oilseed
- Is a centrifugal extractor
- Employs only counter-current extraction
Q18 | In case of absorption, both the operating and equilibrium lines will be straight for
- Isothermal operation
- Dilute solutions
- Dilute solutions and isothermal operation
- None of these
Q19 | The most economical range of absorption factor is
- 0 to 0.5
- 0 to 3
- 1.25 to 2
- 5 to 15
Q20 | In the constant rate period of the rate of drying curve for batch drying,
- Cracks develop on the surface of the solid
- Rate of drying decreases abruptly
- Surface evaporation of unbound moisture occurs
- None of these
Q21 | Back-trapping in a distillation column
- Increases tray efficiency
- Decreases tray efficiency
- Reduces pressure drop
- Is desirable, as it provides improved vapour-liquid contact
Q22 | Rose oil is extracted from rose leaves using __________ distillation.
- High pressure
- Low pressure
- Extractive
- Steam
Q23 | The value of NA/(NA + NB), for steady state equimolal counter diffusion of two gases 'A' and 'B' is
- 1
- ?
- 0.5
- 2
Q24 | Pick out the wrong statement pertaining to the rotary dryer.
- Flights (located in the inside shell of rotary dryer) lift the material being dried and shower it down through the current of hot air/gases. It extends from the wall to a distance which is about 8-12% of the inside diameter of shell
- Hold up of a rotary drier is defined as the fraction of the dryer volume occupied by the solid at any instant. The best performance for rotary drier is obtained, when the hold up is in the range of 0.05 to 0.15
- Rotary dryer is suitable for drying sticky material
- Recommended peripheral speed of a rotary drier is in the range of 10 to 30 metres/minute
Q25 | Which of the following is not a unit of mass transfer co-efficient?
- Moles transferred/ [(time) (area) (mole fraction)]
- Moles transferred/ [(time) (area) (mass A/mass B)]
- Moles transferred/ [(time) (area) (pressure)]
- None of these