Question

3-In distillation, the number of plates depends on:

Distillate composition

Bottom’s product composition

Relative volatility

All of them

4-In order to have unbounded water:

The solid should have holes

The solid should be hygroscopic

Relative humidity should be lower than 100%

None of them

Answer 1

3. In distillation, the required number of plates depends on all the options given.

See, if we want a desired distillate composition with high purity of more volatile components, then the degree of mass transfer should be more. Therefore we will require more stages for contacting gas and liquid. Same goes for the bottom product composition.Bottom product should have less amount of more volatile component in it.

Coming to relative volatility, if the relative volatility of two components in the feed is less then the difference in their boiling points will be less. This makes distillation process quite hectic. As a result more no. of stages are required in order to separate the two components.

So all of them is the correct option.

4. Let's first talk what unbounded moisture or water is. The unbounded moisture is the moisture present on the surface if the solid which exerts equilibrium vapor pressure equal to the vapor pressure of pure liquid at same temperature. This means the relative humidity of unbounded moisture is 100%. The movement of unbounded moisture is not hindered or affected by the solid on which it is present. Now let's check the options.

If the soild has holes in it, then the movement of the moisture present gets confined to only direction. This means presence of holes will affect the movement of the moisture. So this option gets eliminated.

A hygroscopic solid tends to aborb moisture from it's surrounding. So if the solid happens to be hygroscopic, the unbounded moisture will also get absorbed into the bulk of solid. This again affects the movement of the water. So this option also gets eliminated.

As we already discussed unbounded moisture or water always has a relative humidity of 100% because it's equilibrium vapor pressure is equal to that of pure liquid. So this option also gets eliminated.

Therefore, none if them is the correct option.