Property comparison: “The freezing point of carbon dioxide is equal to the boiling point of refrigerant R-12.” State whether this statement is correct.

Introduction / Context:Knowing basic thermophysical properties of common refrigerants and gases is important for safe design and selection. This statement compares the freezing point (or sublimation point) of CO₂ with the normal boiling point of R-12.

Given Data / Assumptions:

• Carbon dioxide (CO₂) at 1 atm sublimates at about −78.5 °C and has a triple point near −56.6 °C.
• Refrigerant R-12 (dichlorodifluoromethane) normal boiling point at 1 atm is about −29.8 °C.
• Standard pressure comparison unless otherwise specified.

Concept / Approach:Compare characteristic temperatures at standard conditions. The CO₂ freezing/sublimation and R-12 boiling points are very different, separated by tens of degrees Celsius, so they are not equal.

Step-by-Step Solution:Identify CO₂ temperature: approximately −78.5 °C at 1 atm (sublimation).Identify R-12 boiling point: approximately −29.8 °C at 1 atm.Compare: −78.5 °C ≠ −29.8 °C → statement is false.

Verification / Alternative check:Consult standard property tables: the large difference is consistent across reputable sources and is independent of unit system.

Why Other Options Are Wrong:

• Conditional “correct” options presume pressure/mixture effects; the statement is absolute and thus incorrect.

Common Pitfalls:Confusing sublimation (solid to gas) with melting/freezing or boiling points; overlooking pressure dependence of phase change temperatures.

Final Answer:Incorrect