When the liquid phase and vapour phase of a binary system obeys Raoult's and Dalton's law respectively, the relative volatility is the ratio of

ANS:A - vapour pressure of component A to that of component B.

In a binary system where the liquid phase obeys Raoult's law and the vapor phase obeys Dalton's law, each component contributes independently to the total vapor pressure of the system. The vapor pressure of each component (A and B) in the liquid phase is determined by Raoult's law, which states that the partial pressure of a component in the vapor phase is directly proportional to its mole fraction in the liquid phase and its vapor pressure at that temperature. Now, considering the relative volatility (𝛼α), it represents the tendency of one component (let's say component A) to preferentially vaporize compared to another component (component B) at a given temperature. Mathematically, it is expressed as: 𝛼=𝑃𝐴𝑃𝐵α=PB​PA​​ Where:

• 𝑃𝐴PA​ is the vapor pressure of component A.
• 𝑃𝐵PB​ is the vapor pressure of component B.

So, when we say "relative volatility is the ratio of the vapor pressure of component A to that of component B", we mean that 𝛼α represents how much more easily component A vaporizes compared to component B. If 𝛼>1α>1, it indicates that component A has a higher tendency to vaporize than component B. Conversely, if 𝛼<1α<1, it means that component B vaporizes more readily than component A.