8.3.8 (HL)—Photochemical smog

Photochemical smog forms when sunlight drives reactions between primary NOx and VOCs, producing secondary PANs and tropospheric ozone.

Name both the emitted precursors and the atmospheric condition. Smog is a chemical transformation, not simply a visible mixture of whatever came from a tailpipe.

Vehicle NOx plus solvent VOCs on a sunny afternoon can produce ozone and PANs downwind of the source.

Primary NOx and VOCs; PANs and ozone belong on the secondary-product side.

Ozone in photochemical smog is secondary, not emitted in the same way as NOx or VOCs.