Which refrigerant sublimates at 14.7 psia?

The correct answer is CO2, as this refrigerant sublimates at 14.7 psia, which is equivalent to atmospheric pressure at sea level. Sublimation is the process where a substance transitions directly from a solid to a gas without going through the liquid phase.

In the case of CO2, at pressures around 14.7 psia, it does not have a liquid state; instead, it exists in a solid form (dry ice) that converts directly to a gas when exposed to atmospheric conditions. This characteristic makes CO2 unique among common refrigerants, which typically function as liquids under standard atmospheric pressure and do not transition to a gas directly from a solid form without going through a melting process first.

Understanding the properties of different refrigerants, especially their phase behaviors under varying pressures, is essential in refrigeration practices and applications. CO2's sublimation point at this pressure distinguishes it from more conventional refrigerants, which typically operate within specific pressure and temperature ranges but remain liquids at 14.7 psia, leading to different operational characteristics and applications.