All gases except ____________ demonstrate a cooling phenomenon when throttled at atmospheric temperature and pressure?
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Answer: D. Hydrogen
Explanation
Hydrogen has a negative Joule-Thomson coefficient at standard room temperature and atmospheric pressure. When throttled under these conditions, its temperature increases rather than decreasing like most gases. This unique thermodynamic behavior stems from its extremely low molecular weight and weak forces. The Joule-Thomson effect defines whether a gas cools or warms during an isenthalpic expansion process. Most common gases lie below their inversion temperatures at room conditions and thus cool down. Hydrogen inversion temperature is well below ambient levels, making its coefficient negative at room temperature.
Safety protocols in hydrogen fueling stations must account for unexpected heating during pressure drops. Cryogenic technicians must pre-cool hydrogen below 200 Kelvin before utilizing throttling for liquefaction. Understanding gas specific Joule-Thomson properties prevents equipment damage during high pressure handling. Oxygen exhibits a positive Joule-Thomson coefficient at room temperature and cools down upon throttling. Nitrogen cools when throttled at atmospheric conditions due to its positive Joule-Thomson coefficient. Air behaves like its primary components, oxygen and nitrogen, experiencing standard cooling during expansion.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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