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CH304K Chapter 1 Notes part 3 (1)

CH304K Chapter 1 Notes part 3 (1) - CH304K Chapter 1 Notes...

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CH304K Chapter 1 Notes part 3 Chemically: - where did the pollutants come from? - how do they act as pollutants? A lot of the US’s pollution comes from: energy generation or transportation Why? Pollution from Energy Generation: Burn coal: makes energy. Use to generate electricity (see Ch 4, 7). Coal contains sulfur: which combusts to sulfur dioxide: S + O 2 o SO 2 Coal contains minerals that don’t combust, or, form solid products - i.e., forms Ash (PM) PM is an air pollutant, but: Ash particles also speed up or CATALYZE these other reactions..* *Sulfur dioxide combines with more oxygen to make sulfur trioxide: 2SO 2 + O 2 o 2SO 3 * Sulfur trioxide combines with water in humid air to make a fog or fine mist of sulfuric acid: SO 3 + H 2 O o H 2 SO 4 This acid damages lungs and contributes to acid rain. Coal fired power stations make much of the SO x and also form NO x but are not the only culprit for NO x ! Pollution from Transportation: i.e., the internal combustion engine Many engines burn gasoline (a hydrocarbon). Sulfur dioxide not produced in significant amounts: - gasoline contains almost no sulphur. Not the case for diesel engines (hence labels on diesel pumps!)! Engine exhaust pipe emissions contain: carbon monoxide, NO x , partly burnt fuel components (VOC’s), PM & lead(outside the US). Engine emissions are also responsible for tropospheric ozone and some smog. carbon monoxide: forms from incomplete combustion of carbon: 2C + O 2 o 2CO oxides of nitrogen (NO x ): NO forms from nitrogen and oxygen gas present in the air sucked into the combustion chamber and the extreme heat of the combustion: N 2 + O 2 o 2NO NO converts back and forth to NO 2 by a complex set of reactions (see below) NO 2 forms in urban areas from reaction of NO with ground level ozone: NO + O 3 o NO 2 + O 2 But it can break down in the sun (see later) to reform NO!!!
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