A superheated vapor is a:

• A. Dry vapor above the saturation temperature
• B. Wet vapor at the saturation temperature
• C. Dry vapor below the saturation temperature
• D. Saturated mixture with liquid present

Answer: (A)

A superheated vapor is a vapor that has been heated above the temperature at which it would begin to condense (the saturation temperature) for its pressure. When a vapor is pushed past this point, any liquid would have already fully vaporized, so the substance exists as a dry gas with no liquid droplets. That’s why the best description is a dry vapor above the saturation temperature. A wet vapor at the saturation temperature would contain liquid droplets, which isn’t the case for a superheated state. A dry vapor below the saturation temperature isn’t stable, since cooling would cause condensation. A saturated mixture with liquid present describes vapor and liquid in equilibrium, not a pure superheated gas.