Which of the following best explains why hydrofluoroolefin (HFO) refrigerants are less flammable than hydrocarbon refrigerants?

• A. HFO refrigerants have higher vapor pressures, making them less likely to ignite.
• B. HFO refrigerants have lower boiling points, preventing combustion.
• C. HFO refrigerants are more reactive with oxygen, which suppresses flames.
• D. HFO refrigerants contain fluorine atoms, which increase molecular stability and reduce flammability.

Answer: (D)

Verified step by step guidance

1. Understand that flammability in refrigerants is related to how easily the molecules can react with oxygen to sustain combustion.
2. Recognize that hydrofluoroolefin (HFO) refrigerants contain fluorine atoms, which are highly electronegative and form strong bonds with carbon atoms.
3. Know that the presence of fluorine atoms increases the molecular stability of HFOs by making the carbon-fluorine bonds less reactive compared to carbon-hydrogen bonds in hydrocarbons.
4. Realize that this increased stability reduces the tendency of HFO molecules to break apart and react with oxygen, thereby lowering their flammability.
5. Conclude that the key reason HFO refrigerants are less flammable than hydrocarbons is due to the fluorine atoms enhancing molecular stability and reducing the likelihood of combustion.