Which of the following refrigerants is a fluorinated compound whose number starts with a 4?

The correct answer identifies a category of refrigerants known as zeotropic refrigerants, which are mixtures that display varying thermal properties when mixed. In the context of refrigerants classified under the A4 category—meaning they consist of fluorinated compounds with numbers starting with a 4—zeotropic refrigerants distinguish themselves by their ability to offer efficient cooling at varying temperature and pressure conditions.

When discussing refrigerants, the classification is essential for understanding their behavior in different systems. Zeotropic refrigerants are particularly significant because they can operate more efficiently in certain applications, especially those that require precise temperature control.

Fluorinated compounds exhibit characteristics desirable for refrigeration, including low toxicity, low flammability, and non-ozone-depleting properties, making zeotropic mixtures widely used in modern refrigeration systems. This classification represents a deliberate choice in the evolution of refrigerant technology to meet both environmental and operational needs.