Mass Transfer Set 1

Q1 | According to the Fenske equation, what will be the minimum number of plates required in a distillation column to separate an equimolar binary mixture of components A and B into an overhead fraction containing 99 mol% A and a bottom fraction containing 98 mol% B ? Assume that relative volatility (?AB = 2) does not change appreciably in the column.

Q2 | With increase in the mass velocity of the gas, the rate of drying during the constant rate period __________, if the conduction and radiation through the solid are negligible.

Q3 | During the constant rate period of drying of a solid,

Q4 | Large scale drying of wheat is done in a __________ dryer.

Q5 | Humidification involves mass transfer between a pure liquid phase and a fixed gas, which is

Q6 | With increase in temperature, the leaching rate increases due to

Q7 | As the reflux ratio, in a continuous counter-current extraction is increased, the number of stages

Q8 | In distillation where q is defined as the moles of liquid flow in the stripping section per mole of feed introduced, for saturated liquid feed

Q9 | Large scale drying of sugar is done in a __________ dryer.

Q10 | Though, theoretically the adsorption & desorption isotherms is expected to coincide but sometimes at least a part of the isotherms does not coincide and this phenomenon is known as adsorption hysteresis. In such cases, the desorption equilibrium pressure is __________ that obtained for adsorption.

Q11 | H2S 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 is given by, y = 1.5 x. The bulk concentration of H2S has to be reduced from 0.05 to 0.001 mole fraction in the gas side. The height of the tower (in metres) corresponding to an operating line given by, y = 5x + 0.001 is

Q12 | Reboiler is considered as one theoretical plate, because

Q13 | In an absorption column, the flooding velocity for random packing is __________ that for stacked/regular packing.

Q14 | Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 × 10-3 kg mole/m2 .s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.01 respectively is:

Q15 | In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the __________ number.

Q16 | When the gas to be dissolved in liquid is a/an __________ then normally co-current adsorber are used.

Q17 | Unsaturated air (with dry and wet bulb temperatures being 35 and 25°C respectively) is passed through water spray chamber maintained at 35°C. The air will be

Q18 | __________ equation applies to diffusivities in liquids.

Q19 | Mass transfer co-efficient is defined as

Q20 | The relative volatility of a binary mixture at constant temperature __________ the total pressure.

Q21 | Large quantity of silica gel is normally dried in a __________ dryer.

Q22 | The mass transfer co-efficient for a solid sphere of radius 'a' dissolving in a large volume ofquiescent liquid, in which „D’ is the diffusivity of solute, is

Q23 | The value of „L/mG’ ratio for economical absorption operation ranges from

Q24 | Cox chart, which is useful in the design of distillation column particularly for petroleumhydrocarbons, is a plot of (where, P = vapor pressure, T = temperature).

Q25 | In a single stage extraction process, 10 kg of pure solvent S (containing no solute A) is mixed with 30 kg of feed F containing A at a mass fraction xf = 0.2. The mixture splits into an extract phase E and a raffinate phase R containing A at xB = 0.5 and xR = 0.05 respectively. The total mass of the extract phase is (in Kg)