Catalytic converters reduce nitrogen oxides in exhaust

Steps:

• Identify main pollutants in car exhaust: carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx like NO2).
• Recall catalytic converter function: uses platinum, palladium, rhodium to catalyze reactions converting pollutants to less harmful gases.
• Note NOx reduction: NO2 + CO → NO + CO2, then 2NO → N2 + O2, removing NO2.
• Confirm NO2 is specifically targeted as part of NOx emissions control.

Why D is correct:

• Nitrogen dioxide (NO2) is reduced to nitrogen gas (N2) and oxygen (O2) via the converter's three-way catalyst, directly removing it from exhaust per environmental regulations.

Why the others are wrong:

• A. Carbon dioxide is a product of combustion and converter reactions, not removed.
• B. Carbon monoxide is oxidized to CO2, but the question focuses on NO2 removal in this context.
• C. Hydrocarbon vapour is oxidized to CO2 and H2O, but not the primary gas highlighted here.

Final answer: D