ANS:B - decreases

In a counter-current extractor, as the axial mixing increases, the extraction efficiency generally decreases. Here's why: Counter-current extraction relies on maintaining a strong concentration gradient between the solvent and the feed solution as they flow in opposite directions. This gradient allows for efficient mass transfer between the two phases. However, if axial mixing increases, it leads to increased dispersion of the solute within the solvent phase, reducing the effectiveness of the concentration gradient and decreasing extraction efficiency. Increased axial mixing causes the solute to be dispersed over a larger volume of the solvent phase, reducing the driving force for mass transfer and increasing the likelihood of back-mixing. As a result, the extracted solute becomes more diluted in the solvent phase, leading to lower extraction efficiency. Therefore, as axial mixing increases in a counter-current extractor, extraction efficiency typically decreases.