Air and air quality

Nitrogen and oxygen from the air react at high temperatures inside the car engine. This extreme heat provides the energy necessary to break the strong bonds in nitrogen and oxygen molecules, allowing them to combine and form nitrogen oxides.

Nitrogen oxides contribute to acid rain. They dissolve in atmospheric moisture, forming acids that fall as precipitation, harming ecosystems and damaging infrastructure.

To test for ammonium ions, add aqueous sodium hydroxide (NaOH) to the sample and gently heat the mixture. Ammonium ions react with hydroxide ions to release ammonia gas.

A positive result for the ammonium ion test is when the damp red litmus paper turns blue. This indicates the presence of alkaline ammonia gas, confirming the presence of ammonium ions.

Unburnt hydrocarbons contribute to smog and can have carcinogenic effects. They react with other pollutants in the presence of sunlight to form ground-level ozone, a major component of smog.

A catalytic converter reduces pollution from car exhaust. It converts harmful pollutants like carbon monoxide (CO), nitrogen oxides (NOx), and unburnt hydrocarbons into less harmful substances like carbon dioxide (CO2), nitrogen (N2), and water (H2O).

Sodium hydroxide is used to release ammonia gas from ammonium compounds, which can then be tested using damp red litmus paper (it turns blue). If a carbonate impurity is present, limewater (calcium hydroxide solution) can be used to test for any evolved carbon dioxide gas, which will turn the limewater cloudy.