The table shows results from a harbour safety inspection of fuel canisters used on small boats. Each canister contains a liquefied hydrocarbon gas. A techni...
Question 1 Report
The table shows results from a harbour safety inspection of fuel canisters used on small boats. Each canister contains a liquefied hydrocarbon gas. A technician released equal volumes of gas into separate chambers and supplied the same amount of oxygen. Carbon monoxide was measured after ignition. The canisters must not be used in cabins unless there is good ventilation because carbon monoxide is poisonous.
| condition in chamber | appearance of flame | carbon monoxide concentration / ppm |
|---|---|---|
| excess oxygen | blue | 0 |
| limited oxygen | yellow | 180 |
| very limited oxygen | yellow, smoky | 620 |
(a) State the name given to a reaction in which a hydrocarbon burns with excess oxygen. [1]
(b) Give the two substances formed when butane undergoes this reaction. [2]
(c) Explain why carbon monoxide is detected when the oxygen supply is limited. [2]
(d) Use Table 1 to describe the change in carbon monoxide concentration as less oxygen is available. [2]
(e) Suggest one action a boat owner could take to reduce the risk from carbon monoxide when using a gas stove. [1]
Answer Details
(a) Burning a hydrocarbon with excess oxygen is called complete combustion. [1]
(b) Butane undergoing complete combustion forms carbon dioxide and water. [2]
(c) With limited oxygen, there is insufficient oxygen for complete combustion. Carbon is then oxidised to carbon monoxide rather than carbon dioxide. [2]
(d) Carbon monoxide concentration increases as oxygen availability decreases: it rises from 0 ppm in excess oxygen to 180 ppm in limited oxygen, then to 620 ppm in very limited oxygen. [2]
(e) The owner could ventilate the cabin by opening vents or windows. Servicing the stove or fitting a carbon monoxide alarm would also reduce risk. [1]
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