Moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the __________ moisture.

ANS:A - unbound

Unbound" moisture isn't a commonly used term in this context. However, I can provide some clarification. When we talk about moisture in solids, we often refer to two main types: free moisture and bound moisture.

1. Free Moisture: This refers to the moisture present in a solid material that is not chemically bound to the material. It exists as surface moisture or water absorbed within the pores of the solid. Free moisture can be readily evaporated or removed under ambient conditions, and its vapor pressure equals the vapor pressure of pure water at the same temperature.
2. Bound Moisture: Bound moisture, on the other hand, refers to the moisture that is chemically or physically bound to the solid material. It is tightly held within the structure of the material and cannot be easily removed without altering the structure of the material. Bound moisture typically has a lower vapor pressure than free moisture and requires more energy or specific conditions to be released from the solid material.

"Unbound" moisture seems to imply a similar concept to free moisture, referring to moisture that is not tightly bound to the solid. However, "free moisture" is the more commonly used and recognized term in this context. If you have a specific context or usage of "unbound moisture" in mind, please let me know, and I can provide more tailored information.