Combusting pure carbon entirely in oxygen produces flue gas containing 70% CO2, 20% CO, and 10% O2; the percent excess oxygen applied equals __________________?
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Answer: C. 0
Explanation
Flue gas containing carbon monoxide indicates that carbon did not achieve complete oxidation to carbon dioxide. The presence of unburned carbon monoxide means that available oxygen was insufficient to oxidize all fuel completely. Since no free oxygen appears in the exhaust analysis alongside carbon monoxide, the excess oxygen percentage is mathematically zero. Combustion stoichiometry requires all carbon to form carbon dioxide and all hydrogen to form water under ideal conditions. Excess oxygen is defined as the percentage of unreacted oxygen remaining in the flue gas relative to theoretical requirements. Incomplete combustion reactions generate carbon monoxide intermediates that consume available oxygen without reaching completion.
Twenty percent excess oxygen is impossible when carbon monoxide is present and free oxygen is completely absent from the gas. Twelve point five percent is incorrect because the presence of carbon monoxide proves that oxygen was deficient, not in excess. Ten percent is incorrect because free oxygen must be measured in the flue gas to calculate a positive excess oxygen percentage.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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