Acids in the Atmosphere - Unit 4C Unit 4.C. 1 Acid Rain

How do we measure acidity? pH scale - power of ‘H’ All acids contain easily removable H+ Usually the ‘H’ is in the front of the formula HCl, H 2 SO 4, HNO 3 HCl --> H +1 + Cl -1 In H 2 O, the H comes off also

pH Which pH is neutral? Which pH is acidic? Which pH is basic?

What is acid rain? Fog, sleet, snow, or rain with pH < 5.6 Natural rain without pollution is pH ~ 5.6 Why isn’t it neutral? Rainwater isn’t pure - it contains dissolved gases CO 2 is part of the respiration process CO 2 + H 2 O H 2 CO 3 This is a weak acid

Nonmetal oxides react with water to form acids SO 2 + H 2 O H 2 SO 3 SO 3 + H 2 O ________ ? 2NO 2 + H 2 O HNO 3 + HNO 2 Sources of sulfur and nitrogen oxides include volcanoes, forest fires and lightning Burning coal and fossil fuels also produce these oxides

pH measurements across the US

ChemQuandry Maine has no coal-fired power plants and relatively few residents. However, the average pH of the precipitation in the state is lower than that of unpolluted rainfall. Why might this be?

Results of Acid Rain Lowers the pH in lakes and streams enough to kill fish eggs and other aquatic life. Damages plants by leaching minerals from the soil that the plants need to grow healthy Additional detioration of buildings and other structures that contain: Metals, limestone, or concrete

Addressing Acid Rain Clean Air Act of 1990 Restriction on amounts of SO 2 emitted from fossil-fuel power plants Use of more expensive low-sulfur coal Use of scrubbers to remove SO 2 from smokestack

Addressing Acid Rain NO and NO 2 are referred to as NOx From the reaction of N 2 with O 2 at high temps like in internal combustion engines (cars) It is harder to clean up transportation sources of NOx

Acids and Bases Structure and Properties - C.4 & C.5 Acids - hydrochloric - HCl, nitric - HNO 3, sulfuric - H 2 SO 4, acetic acid HC 2 H 3 O 2 Bases - sodium hydroxide - NaOH, potassium hydroxide - KOH, any metal hydroxide -, ammonia - NH 3,

Arrhenius acids / bases acids produce hydrogen ions - H + in aqueous (water) solutions The H + from the acid then bonds to water to produce the hydronium ion, H 3 O + H + + H 2 O --> H 3 O + bases produce hydroxide ions, OH - in aqueous solutions, they simply dissolve in water KOH + H 2 O --> K + (aq) + OH - (aq) The metal ion and hydroxide ion are separated

Neutralization How do you neutralize a solution? mix the same amounts of acid and base. It no longer behaves as an acid or a base! acid + base --> a salt + water (neutral solution) HCl + NaOH --> NaCl + H 2 O what separated and what formed? Let’s try HBr and KOH ! Homework: Complete 4.C.5 questions 1-4 pg 372