Is nitrogen a more efficient inerting material than carbon dioxide because nitrogen has a higher molar heat capacity?

Is nitrogen a more efficient inerting material than carbon dioxide because nitrogen has a higher molar heat capacity?

• A. False
• B. Not Applicable
• C. True
• D. Not Sure

Answer: (C)

The ability of an inerting gas to suppress a flame isn’t determined by having the higher molar heat capacity alone. What matters is how effectively the gas can displace oxygen and dilute the flammable mixture to below the flammable limit, along with safety and practicality in a given space. In terms of molar heat capacity, carbon dioxide actually has a higher Cp,m than nitrogen (roughly 37 J/mol·K for CO2 versus about 29 J/mol·K for N2). This means CO2 can absorb more heat per mole, not nitrogen. So the idea that nitrogen is more efficient because it has the higher molar heat capacity is not correct.

The ability of an inerting gas to suppress a flame isn’t determined by having the higher molar heat capacity alone. What matters is how effectively the gas can displace oxygen and dilute the flammable mixture to below the flammable limit, along with safety and practicality in a given space. In terms of molar heat capacity, carbon dioxide actually has a higher Cp,m than nitrogen (roughly 37 J/mol·K for CO2 versus about 29 J/mol·K for N2). This means CO2 can absorb more heat per mole, not nitrogen. So the idea that nitrogen is more efficient because it has the higher molar heat capacity is not correct.