Refrigerant property recall — normal boiling point of R-12 (dichlorodifluoromethane) Is the approximate normal boiling point of R-12 about −30 °C under 1 bar atmospheric pressure?

Introduction / Context:Older vapor-compression systems frequently referenced R-12 (CCl2F2) in teaching materials. Knowing its normal boiling point helps understand why it was suitable for subzero evaporator temperatures at moderate suction pressures.

Given Data / Assumptions:

• Normal boiling point refers to saturation at approximately 1 bar (standard atmospheric pressure).
• R-12 property value commonly cited near −29.8 °C.

Concept / Approach:A refrigerant with a low normal boiling point can evaporate at low temperatures while maintaining manageable pressures, enabling efficient refrigeration for comfort and medium-temperature applications.

Step-by-Step Solution:

Verification / Alternative check:Reference pressure–temperature charts for R-12 show saturation around −30 °C at approximately 1 bar absolute.

Why Other Options Are Wrong:Values like −10 °C or above 0 °C would imply much higher saturation temperatures inconsistent with known R-12 data; restricting to “reduced pressure only” misunderstands the definition of normal boiling point.

Common Pitfalls:Confusing R-12 with R-22 or R-134a, which have different boiling points; always confirm the specific refrigerant.

Final Answer:

True