Question 66 AEL01 - Assistant Engineer - Limited

The Correct Answer is B. ### Explanation for Option B (Saturated Condition) The condition where a vapor is in equilibrium with its liquid phase and both are at the same temperature, specifically the boiling point corresponding to the pressure, is defined as the **saturated condition**. * **Saturation** describes the state where the liquid is just about to vaporize, and the vapor is just about to condense, with the rates of evaporation and condensation being equal. * The vapor in this state is called **saturated vapor**, and the liquid is called **saturated liquid**. * Since the vapor was generated directly from the boiling liquid and remains in contact with it at that specific temperature (the saturation temperature), they exist together at equilibrium in a saturated mixture. ### Explanation for Why Other Options Are Incorrect **A) critical state** The critical state refers to a specific point (the critical point) where the saturated liquid and saturated vapor lines meet on a phase diagram. At this point, the liquid and vapor phases become indistinguishable. The scenario described in the question—vapor in contact with boiling liquid—is the **saturated condition** along the saturation line, not the single, distinct **critical state**. **C) sensible contact** "Sensible" heat or contact refers to heat transfer that results in a temperature change of the substance (e.g., heating liquid water from $20^\circ\text{C}$ to $90^\circ\text{C}$). The condition described involves a phase change (boiling/condensation) at a constant temperature (the saturation temperature). While contact is present, describing the thermodynamic *state* as "sensible contact" is not standard terminology and does not accurately capture the equilibrium condition. **D) latent contact** "Latent" heat refers to the heat involved in a phase change occurring at a constant temperature (like boiling or condensation). While the heat exchange involved in maintaining the equilibrium is latent heat, "latent contact" is not a recognized thermodynamic term used to describe the state of the system (the phase equilibrium). The correct term for the state is the **saturated condition**.