2.0 – ACIDS AND BASES - PowerPoint PPT Presentation

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  1. 2.0 – ACIDS AND BASES

  2. Which of the following are acids? Which are bases?

  3. I. Acids and Bases A. Identifying Acids and Bases • Solutions can be classified as being either an acid, base or a neutral solution. Acid – substance which dissolves in water to have a pH below 7 Ex. Fruits, vinegar Bases – substance which dissolves in water and have a pH higher than 7 Ex. Soaps, hair conditioner

  4. I. Acids and Bases • pH scale– measures the concentration of hydrogens in a solution >Every decrease of 1 pH means the concentration is 10x different Ex. Lemon is a pH of 2, tomatoes are a pH of 4 How many more times acidic is a lemon than a tomato?

  5. I. Acids and Bases ACID 1.0 7.0 14.0 NEUTRAL BASE Stomach Distilled H20 Drain cleaner acid Baking soda milk

  6. I. Acids and Bases • Indicators – chemicals that indicate an acid or base by indicating the pH by changing color. Ex. Bromothymol blue, phenolphtalein, litmus paper, universal indicator

  7. I. Acids and Bases

  8. I. Acids and Bases Common Acids (memorize) HCl – hydrochloric acid H2SO4 – sulfuric acid Common Bases (memorize) NaOH –sodium hydroxide Ca(OH)2 – calcium hydroxide

  9. I. Acids and Bases Check your understanding: 1. Is H2SO4 an acid or base? • Is KOH an acid or base? • Is NaCl an acid or base? • If a solution turns red litmus blue, it is an acid or base? • Which is a more concentrated base – a pH of 8 or 10? • Would HNO3 turn bromothymol yellow or blue?

  10. I. Acids and Bases B. Reaction of Acids and Bases 1) Neutralization – a reaction when an acid and base are mixed, causing the pH becomes close to 7 acid + base  water + salt 2) Concentration – you can tell between two acids, which is more concentrated based on its rate of reaction KEY: The more concentrated, the stronger its reaction OR The stronger the acid, the more base it takes to neutralize

  11. I. Acids and Bases • Causes of Acid Precipitation (rain or snow) -When driving our vehicles and through industrial processes we create acid deposition through combustion • When burned, the following form acid precip: a) Sulfur oxides (SO2, SO3)  Sulfurous & sulfuric acid b) Nitrous oxides (NO2)  nitrous & nitric acids c) Carbon dioxide (CO2)  forms carbonic acid in water • Acid rain falls and enters our lakes, making them too acidic for organisms to live in

  12. What area of Canada and the US have the lowest measured pH? Why do you think this is?

  13. Here are the effects of an acidified ecosystem on the natural environment: http://www.ec.gc.ca/air/default.asp?lang=En&n=7E5E9F00-1 Environmental Canada

  14. Sudbury The Sudbury region has a well-known history for very high local SO2 emissions and associated acid deposition. Furthermore, it has a broad sensitivity to acid rain. The degree of historical damage to the landscape, combined with efforts of the Ontario government and industry to improve conditions, makes the Sudbury area an unintentional but important "experiment" on a whole ecosystem acidification and recovery process. Of the 7000 lakes estimated to have been damaged by smelter emissions, most are located in the hilly forested areas, underlain by granite bedrock, northeast and southwest of Sudbury. As a result, sport fish losses from acidification in this area have also been heavy. In fact, most of Canada's well-documented cases of fisheries losses from acid rain are in the Sudbury area (not forgetting, of course, the losses of Atlantic salmon from Nova Scotia rivers and some sports fish losses in areas of Quebec).

  15. Over 35 years ago, scientists began studying the lakes and ponds near Sudbury. Since then, a vast amount of information has been collected that has clearly established the damaging effect of smelter emissions on the chemistry and biology of water bodies. This information has since been widely used throughout Canada and the rest of the world in the debate for cleaner air. Dramatic chemical improvements in Sudbury area lakes have been observed following substantial reductions in local smelter emissions. Between 1980 and 1997, Inco and Falconbridge, the two major producers of smelter emissions in the Sudbury area, reduced theirSO2 emissions by 75% and 56% respectively. Overall, the widespread chemical and biological improvements seen in lakes of the Sudbury area demonstrate the resiliency of aquatic systems and provide strong support for the use of emission controls to combat aquatic acidification. However, many area lakes are still acidic and contaminated with metals.

  16. Major Sulphur Dioxide (SO2) sources in Sudbury, Ontario (kilotonnes)

  17. I. Acids and Bases D. Fixing/Preventing Acid Deposition Effects • Liming – the process of neutralizing a lake by adding lime (calcium hydroxide – Ca(OH)2) to the lake > mostly in eastern Canada >Western Canada lakes have a limestone base and are naturally neutralized. 2) Catalytic Converters – on vehicles to reduce NOx and CO2 emissions from a vehicle 3) Scrubbers – device which removes SO2 emissions from industrial processes (uses lime!) such as coal burning stations Video: Acids and Bases