# Practice Test: Question Set - 26

**1. If**

*R*is the minimum reflux ratio, the optimum reflux ratio may be around ___________{m}*R*._{m}- (A) 1.2 to 1.5

- (B) 2.5 to 3

- (C) 3 to 4

- (D) 5

**2. Adsorption is a unit operation which generally involves __________ systems.**

- (A) Liquid-solid

- (B) Gas-solid

- (C) Fluid-solid

- (D) Solid-solid

**3. Surface renewal model of mass transfer was enunciated by**

- (A) Toor and Marcello

- (B) Fick

- (C) Danckwerts

- (D) Stefan

**4. Agitator is provided in a crystallizer for**

- (A) Avoiding deposition
on cooler surfaces

- (B) Formation of nuclei

- (C) Crystal growth

- (D) All (a), (b) and (c)

**5. Which of the following adsorbent is used to decolourise yellow glycerine?**

- (A) Silica gel

- (B) Alumina

- (C) Fuller's earth

- (D) Activated carbon

**6. Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of**

- (A) Mass diffusivity to
momentum diffusivity

- (B) Thermal diffusivity
to mass diffusivity

- (C) Momentum diffusivity
to thermal diffusivity

- (D) None of these

**7. Binary distillation involves the mass transfer by __________ at the gas-liquid interface.**

- (A) Unidirectional
diffusion from liquid to gas phase

- (B) Unidirectional
diffusion from gas to liquid phase

- (C) Either 'a' or 'b'

- (D) A counter diffusion
at an almost equal molar rate

**8. Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number.**

- (A) Sherwood

- (B) Schmidt

- (C) Peclet

- (D) Stanton

**9. Sand is dried in foundries in a _________drier.**

- (A) Rotary

- (B) Fluidized bed

- (C) Vacuum

- (D) Spray

**10. Cox chart is useful in the design of**

- (A) Distillation column

- (B) Evaporator

- (C) Dryer

- (D) Crystallizer

**11. 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) 4

- (B) 8

- (C) 9

- (D) 10

**12. The binary diffusivity in gases and liquids vary respectively as**

- (A)

*T*

^{3/2}and

*T*

- (B)

*T*and

*T*

^{3/2}

- (C) √

*T*and

*T*

^{3/2}

- (D)

*T*

^{3/2}and √

*T*

**13. 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
transferred to B

**14. Pick out the wrong statement pertaining to leaching.**

- (A) Fine solids cannot be
leached in a Pachuca tank

- (B) Door classifier can
be used for leaching of coarse solids

- (C) Vegetable seeds can
be leached in either of Bollman extractor, Rotocel or Kennedy extractor

- (D) Very high temperature
is not needed for the leaching of sugar beet

**15. Azeotropism for ethyl alcohol-water system disappears by**

- (A) Increasing
temperature

- (B) Decreasing pressure

- (C) Increasing pressure

- (D) No means

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