The region (2) in the p-V diagram is known as the "Saturated Liquid-Vapour Region." In thermodynamics, this region is significant as it represents a mixture of liquid and vapor phases in equilibrium. Here's a step-by-step explanation:

1. Understanding the p-V Diagram:
   • The p-V diagram (pressure vs. specific volume) is utilized to represent the phases of a substance.
   • The curve you see is the saturation curve which divides the diagram into different regions.
2. Identifying Regions:
   • (1): Compressed Liquid Region - This is where the substance is entirely in the liquid state, below the saturation curve.
   • (2): Saturated Liquid-Vapour Region - Represents the phase where both liquid and vapor coexist in equilibrium.
   • (3): Superheated/Unsaturated Region - Characterized by the substance being entirely in the vapor state beyond the saturation curve.
3. Ruling Out Other Options:
   • Compressed Liquid Region: It is not region (2) as this is found at lower volumes below the saturation line.
   • Solid-Liquid and Unsaturated Solid Region: These do not appear on the typical p-V diagram for liquids and vapors.
4. Conclusion:
   • Region (2) is indeed the Saturated Liquid-Vapour Region, where a substance exists as a mixture of both phases in equilibrium.

This understanding of the p-V diagram is crucial in thermodynamics as it helps in analyzing the behavior of substances under different conditions.