ANS:B - forms a low boiling azeotrope.

The solvent used in extractive distillation typically does not alter the relative volatility of the original components. In extractive distillation, a third component (the solvent) is added to the system to facilitate the separation of the original components. The solvent interacts preferentially with one of the components, altering its vapor-liquid equilibrium behavior and improving the separation efficiency. Here's how each option applies:

• Solvent of Low Volatility: This is generally not the case. The solvent in extractive distillation is often chosen to have higher volatility than the components being separated to facilitate its removal from the desired product streams.
• Forms a Low Boiling Azeotrope: While the solvent may form an azeotrope with one of the components, it is not necessarily low boiling. The choice of solvent depends on its ability to selectively interact with one component while leaving the other components unaffected.
• Forms a High Boiling Azeotrope: This is also not necessarily true. The solvent may form an azeotrope with one of the components, but the boiling point of this azeotrope could be high or low depending on the specific components and solvent chosen.
• Does Not Alter the Relative Volatility of the Original Components: This is the most accurate statement. The solvent in extractive distillation is selected to preferentially interact with one component, thereby changing its relative volatility compared to the other components. This alteration in relative volatility allows for improved separation efficiency.