Mass Transfer

301.Leaching of sugar from sugar beets is done by

1. Hot water
2. Hexane
3. Dilute H2SO4
4. Lime water

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302.Leaching of uranium ore and gold ore is done in

1. Centrifugal extractor
2. Pachuca tanks
3. Bollman extractor
4. None of these

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303.Leaching rate is independent of the

1. Agitation
2. Temperature
3. Particle size
4. None of these

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304.Lewis number (Le) is

1. Sc × Pr
2. Pr × St
3. Sh × Pr
4. St × Sh

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

1. Mass diffusivity to momentum diffusivity
2. Thermal diffusivity to mass diffusivity
3. Momentum diffusivity to thermal diffusivity
4. None of these

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306.Liquid diffusivity is of the order of _________ cm² /second.

1. 0.01
2. 0.1
3. 10^-5 to 10^-6
4. > 1

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307.Low viscosity absorbent is preferred for reasons of

1. Rapid absorption rates and good heat transfer characteristics
2. Improved flooding characteristics
3. Low pressure drop on pumping
4. All (A), (B) and (C)

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308.Make up water is required in a cooling tower to replace the water lost by

1. Evaporation
2. Drift
3. Blowdown and leakage
4. All (A), (B) and (C)

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309.Make up water is supplied during cooling tower operation to compensate for water losses due to

1. Evaporation
2. Blowdown
3. Entrainment
4. All (A), (B) & (C)

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310.Mass transfer co-efficient 'K' according to penetration theory varies with mass diffusivity as

1. D^0.5
2. D
3. 1/D
4. D^1.5

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