Which class of compounds become vapors at typical atmospheric temperatures and are precursors to ozone formation?

Which class of compounds become vapors at typical atmospheric temperatures and are precursors to ozone formation?

• A. Particulate Matter
• B. Volatile Organic Compounds
• C. Nitrogen Oxides
• D. Sulfur Dioxide

Answer: (B)

Ozone formation in the lower atmosphere relies on reactive organic molecules that readily exist as vapors under typical conditions. These volatile organic compounds have high vapor pressure, so they are present in the gas phase where they can mix with nitrogen oxides and sunlight to drive photochemical reactions. The key sequence is VOCs reacting with hydroxyl radicals to form peroxy radicals, which oxidize NO to NO2. NO2 then photolyzes in sunlight, releasing an oxygen atom that combines with O2 to form ozone. This gas-phase chemistry hinges on the abundance of VOCs in the vapor form, making them the classic precursors to tropospheric ozone. While other substances like nitrogen oxides or sulfur dioxide also influence ozone levels, they aren’t defined by volatility and aren’t the category described here.

Ozone formation in the lower atmosphere relies on reactive organic molecules that readily exist as vapors under typical conditions. These volatile organic compounds have high vapor pressure, so they are present in the gas phase where they can mix with nitrogen oxides and sunlight to drive photochemical reactions. The key sequence is VOCs reacting with hydroxyl radicals to form peroxy radicals, which oxidize NO to NO2. NO2 then photolyzes in sunlight, releasing an oxygen atom that combines with O2 to form ozone. This gas-phase chemistry hinges on the abundance of VOCs in the vapor form, making them the classic precursors to tropospheric ozone. While other substances like nitrogen oxides or sulfur dioxide also influence ozone levels, they aren’t defined by volatility and aren’t the category described here.