Mass Transfer
For the air water system under ambient conditions, the adiabatic saturation temperature and the wet bulb temperature are nearly equal, because

Water has a high latent heat of evaporation
Lewis number is close to unity
Solubility of the components of air in water is very small
They are always equal under all circumstances

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Mass Transfer
An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii)

More number of trays are required but the residue composition remains unchanged
Composition of the residue remains unchanged
Less number of trays are required
More number of trays are required and the residue composition is more dilute in methanol

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Mass Transfer
Fenske's equation for determining the minimum number of theoretical stages in distillation column holds good, when the

Mixture (to be separated) shows positive deviation from ideality
Relative volatility is reasonably constant
Multicomponent distillation is involved
Mixture (to be separated) shows negative deviation from ideality

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