Mass Transfer

261.In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because

1. Temperature is less
2. Total pressure is less
3. Mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition
4. Saturated steam is used for steam distillation

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262.In case of unsaturated air

1. Dew point < wet bulb temperature
2. Wet bulb temperature < dry bulb temperature
3. Both (A) and (B)
4. Neither (A) not (B)

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263.In continuous distillation, the internal reflux ratio (Ri) and the external reflux ratio (Re) are related as

1. R_i = R_e/(1 - R_e)
2. R_i = (1 - R_e)/R_e
3. R_i = R_e
4. R_i = R_e/(1 + R_e)

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264.In distillation columns, the number of bubble caps per tray primarily depends upon the

1. Allowable liquid velocity
2. Allowable gas velocity
3. Allowable gas and liquid velocities
4. Feed composition

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265.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

1. q > 1
2. q < 1
3. q = 1
4. q = 0

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266.In distillation, overhead product contains

1. Only one component
2. Two components
3. Any number of components
4. Only saturated liquid

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267.In extraction, as the temperature increases, the area of heterogeneity (area covered by binodal curve)

1. Decreases
2. Increases
3. Remains unchanged
4. None of these

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268.In extractive distillation, solvent is

1. Added to alter the relative volatility of the mixture
2. Of high volatility
3. Present in overhead stream
4. Of high viscosity to give high tray efficiency

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269.In gas-liquid contact operation, the number of ideal stages, N = (x_a - x_b)/(xb - x^*b). This is true when the stripping factor 'S' is

1. S > 1
2. S < 1
3. S = 1
4. S = ∞

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270.In liquid extraction, if the selectivity is unity, then

1. Separation of the constituents is the most effective
2. No separation will occur
3. Amount of solvent required will be minimum
4. Solvent flow rate should be very low

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