Gas Classified as nitrogen harmless water vapour harmless carbon monoxide pollutant carbon dioxide harmless in small amounts The diagram shows the exhaust g...
Question 1 Report
| Gas | Classified as |
|---|---|
| nitrogen | harmless |
| water vapour | harmless |
| carbon monoxide | pollutant |
| carbon dioxide | harmless in small amounts |
The diagram shows the exhaust gases leaving a petrol engine. The table classifies four of these gases as either harmless or a pollutant. Using the table, which exhaust gas is a pollutant?
Answer Details
A pollutant is a substance released into the air that causes harm. Reading the classification column, nitrogen and water vapour are marked harmless and carbon dioxide is harmless in small amounts, while carbon monoxide is the one classed as a pollutant.
The chemistry behind that classification is worth knowing. Carbon monoxide forms in the engine when there is too little oxygen for complete combustion of the petrol, and it is dangerous because it is colourless and odourless and binds to haemoglobin much more strongly than oxygen does, so the blood can no longer carry enough oxygen.
Nitrogen simply passes through the engine unchanged, and water vapour is harmless. Carbon dioxide contributes to global warming in bulk, but it is not the acutely poisonous exhaust gas.
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