Natural: Lightning fixes N2 + O2 → NO.
N2 + O2 (electric arc) → 2NO
2NO + O2 → 2NO2
Man-made: vehicle combustion, power plants, fertilizers, agriculture. Heavy traffic + industry = NOx + VOCs.
UV light + NOx + VOCs → secondary pollutants:
NOx + VOCs + sunlight → O3 + aldehydes + PAN (peroxyacetyl nitrate)
PAN is toxic, ozone is lung irritant.
NO2 reacts with water:
NOx catalyst role: converts SO2 → H2SO4
Acid rain pH < 5.6, damages ecosystems, corrodes materials.
Harmful effects of NOx: respiratory illness, asthma, lung damage.
Global toll: ~7–8 million deaths/year (air pollution). Children especially vulnerable.
NOx also helps form fine particles and ground-level ozone.
📌 student guidelines & memorization
✓ Write the lightning reaction daily: N2 + O2 → 2NO ; then 2NO + O2 → 2NO2.
✓ Remember acronym: N.A.S. — Nitrogen oxides, Acid rain, Secondary pollutants (PAN, O3).
✓ Link sources: vehicles (NOx) + power plants + agriculture.
✓ Acid rain pH threshold: 5.6 (normal rain), acid rain below that.
✓ NOx acts as catalyst for SO2 → SO3 → H2SO4. “NO helps SO2 die (oxidize)”.
Click an option: correct turns green, wrong turns red. Submit to see score & full key.