Mass Transfer

371.Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the

1. Packing may be crushed due to thermal expansion/contraction of the components of the equipments
2. Pressure drop in the equipment will be very high
3. Viscosity variation of the fluids may cause channelling/flooding
4. None of these

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372.Polar organic compounds are normally used as separating agents for the azeotropic and extractive distillation. Which of the following is the most important factor to be considered for the choice of the separating agent for extractive distillation?

1. Cost
2. Availability
3. Toxicity
4. Selectivity

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373.Ponchon-Savarit method analyses the fractional equipment based on

1. Enthalpy balance only
2. Material balance only
3. Both enthalpy and material balances
4. The assumption of constant molal-overflow

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374.Pore size of the molecular sieve 5A is _________ mm.

1. 5
2. 0.5
3. 0.05
4. 50

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375.Positive deviation from Raoult's law means a mixture whose total pressure is

1. Greater than that computed for ideality
2. Less than that computed for ideality
3. Less than the sum of the vapour pressure of the components
4. None of these

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376.Powdery materials can be guarded against caking tendency on storage by

1. Providing irregular grain size
2. Providing minimum percentage of voids
3. Having maximum possible points of contact
4. None of these

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377.Prandtl number for water at 20°C is about

1. 7
2. 70
3. 0.7
4. 150

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378.Pressure drop through plate tower as compared to that through packed tower, for the same duty will be

1. Less
2. More
3. Equal
4. Either (A) or (B); depends on the packing height

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379.Priming in a distillation column

1. Results from very low gas velocity
2. Is desirable from point efficiency consideration
3. Is characterised by the presence of foam throughout the space between trays
4. Reduces the overall pressure drop

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380.Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the _________ of a fibre.

1. Electrical resistance
2. Thermal conductivity
3. Strength
4. None of these

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