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Chapter 6

Chapter 6. Neutralizing the Threat of Acid Rain; Acid/Base chemistry. Catatan: Diambil dari berbagai sumber. BKMG warns of spike in acid rain levels in Indonesia (24 June 2010, Jakarta Post)

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Chapter 6

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  1. Chapter 6 Neutralizing the Threat of Acid Rain; Acid/Base chemistry Catatan: Diambil dari berbagai sumber

  2. BKMG warns of spike in acid rain levels in Indonesia (24 June 2010, Jakarta Post) Rainwater falling in Indonesia may appear clean, but the weather agency recently released a report showing that it contains dangerous levels of pollutants that are harmful to the environment and human health, The Jakarta Post reported on Thursday. The weather agency categorized polluted rainwater as acid rain with pH levels below tolerable or rainwater pH levels — normally 5.6. The Meteorology, Climatology and Geophysics Agency (BMKG)’s report shows that the acidity of rainwater in Jakarta, Bogor, Pontianak and Manado was among the highest in Indonesia. The data shows that last year the average pH level of rainwater was 4.52 in Jakarta, 4.22 in Manado, North Sulawesi, 4.29 in Pontianak, West Kalimantan and 4.4 in Bogor, West Java.

  3. Acid Rain Deteriorates! At present…. Borobudur ?

  4. Acids and Bases (Arrhenius) Acid = A substance that produces hydrogen ions, H+, in aqueous solution Base = A substance that produces hydroxide ions, OH-, in aqueous solution Neutral Solution = Neither acidic nor basic; Equal concentrations of H+ and OH-

  5. pH scale Remember: pH = -log10 [H+]

  6. Householdammonia Orange

  7. NaHCO3 (aq) + HCl (aq) NaCl (aq) + H2O (l) + CO2 (g) Mg(OH)2 (s) + 2HCl (aq) MgCl2 (aq) + 2H2O (l) NEUTRALIZATION Chemistry In Action: Antacids and the Stomach pH Balance

  8. Measuring the pH of rain

  9. Burning Coal (C135H96O9NS)

  10. How burning coal makes acid rain • S(s) + O2(g) → SO2(g) • Produces SOx and NOx • (SO2 and SO3 , NO and NO2) • Review – Name them!!! • With water in the air they make: • SO2 + H2O g H2SO3 (sulfurous acid) • SO3 + H2O g H2SO4 (sulfuric acid) • 2NO2 + H2O g HNO2 + HNO3 (nitrous, nitric acid)

  11. Rain is naturally acidic • Natural amounts of CO2 are in air. • CO2 + H2O g H2CO3 • Carbonic acid however is a weak acid • Normal rain is about pH of 5.3

  12. Combustion: CH4 + 2 O2 CO2 + 2 H2O + 802 kJ/mol • 2NO2 + H2O g HNO2 + HNO3 (nitrous, nitric acid) • OUT: • CO2 and H2O • Some: • NO and NO2 • (other stuff, such as CO) • IN: • Air • 78% N2 • 21%O2 • Fuel (C &H Source)

  13. Simplified Nitrogen Cycle

  14. Fertilizers can result in: • NO, which leads to acid rain and increased acidity of soil • N2O, a greenhouse gas • NH4+, which can contaminate the water supply

  15. Effect of NOx on lungs

  16. Jakarta Beijing

  17. Your turn: Small changes, big effects • Compare equal volumes of the tomato juice sample, pH=4.5 and milk sample, pH=6.5. Which one is more acidic? How much more acidic? • Answer: Although the pH values differ onl by 2, the sample of tomato juice is 100 times more acidic and has 100 times H+ than the sample of milk

  18. Your turn: Coal Calculation • Assume that coal can be represented by the chemical formula C135H96O9NS. Calculate the fraction and percent (by mass) of sulfur in the coal • A certain power plant burns 1.00x106 tons of coals per year. Assuming the sulfur content calculated in a), calculate the tons of sulfur released per year. • Calculated the tons of SO2 formed from this amount of sulfur Answers: a). 0.00168 or 1.68% b). 16800 tons S

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