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Unformatted text preview: N O 2 + O2 NO reacts with O2, •OH & VOC’s to form NO2: a brown, poisonous, very reactive gas
This gives smog its color.
VOC + •OH A then A + O2 A’ then A’ + NO A’’ + NO2(g)
• OH is present in air naturally (and can be produced as a pollutant too)
PM: any old ‘banger’ that gives off clouds of smoke!
partly burnt hydrocarbon fuel components known as volatile organic compounds (VOC’s).
VOC’s are also present in paints etc. (see indoor air pollution later)
lead: from gasoline which has the tetraethyl lead additive (anti-knocking); on combustion this forms lead
which vaporizes easily. Very rare in the US (only some antique cars) but still present in other countries.
Reducing Auto Pollution
A car exhaust contains: CO, NOx , VOC’s
We would prefer it contained: CO2 , N2 , H2O
Why? What has to happen to the first set of compounds? The Catalytic Converter: Required by law on all new US cars since 1976:
speeds up the process Lead will kill off the catalyst (Pt, Pd, Ni, on the surface of tiny beads) The process isn’t perfect - a poorly
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- Spring '08