In liquid-liquid extraction, if the selectivity is unity, then

• (a) separation of the constituents is most effective

• (b) no separation is possible

• (c) amount of solvent requirement is minimum

• (d) solvent flow rate should be very high

Which of the following is most suitable for extraction from a system having very low density difference?

• (a) mixer-settler extractor

• (b) centrifugal extractor

• (c) pulsed extraction column

• (d) packed extraction column

Radioactive nuclear wastes are treated in

• (a) mixer-settler extractor

• (b) rotating disc contactor

• (c) pulsed extractor

As axial mixing increases in a counter-current extractor, the extraction efficiency

• (a) increases

• (b) decreases

• (c) remains unchanged

Selectivity of a solvent for extraction operation

• (a) is analogous to relative volatility in distillation practice

• (b) must be less than unity

• (c) is 0.5 at the plait point

• (d) none of these

In liquid-liquid extraction, as the temperature increases, the area covered by the bimodal curve

• (a) decreases

• (b) increases

• (c) remains unchanged

• (d) none of these

Operating pressure for liquid extraction should be

• (a) sufficiently high to maintain completely condensed system

• (b) below the vapour pressures of all the components

• (c) equal to the vapour pressure of the most volatile component

• (d) equal to the vapour pressure of the least volatile component

During distribution of a solute between two partially miscible solvents, the selectivity at the plait point is

• (a) zero

• (b 1.0

• (c) less than zero

• (d) very large

For solvent economy in liquid extraction, the distribution coefficient must be

• (a) less than one

• (b) equal to one

• (c) greater than one

• (d) as large as possible

Which of the following operations is more economical for concentration of acetic acid from very dilute aqueous solution?

• (a) evaporation

• (b) solvent extraction

• (c) atmospheric distillation

• (d) drying