Lecture2

Lecture2 - Acids and Bases An acid is any substance that...

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Acids and Bases An acid is any substance that increases the H + concentration of a solution A base is any substance that reduces the H + concentration of a solution
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The pH Scale The pH of a solution is determined by the relative concentration of hydrogen ions Acidic solutions have pH values less than 7 Basic solutions have pH values greater than 7 Most biological fluids have pH values in the range of 6 to 8
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Dissociation of water molecules leads to acidic and basic conditions H 2 O <------> H + + OH - [H + ] = 10 -7 M (25 ˚C) Acid/Base: HCl -------> H + + Cl - pH= log[H + ]
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LE 3-8 pH Scale 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Oven cleaner Household bleach Household ammonia Milk of magnesia Seawater Pure water Human blood Urine Rainwater Black coffee Tomato juice Vinegar, beer, wine, cola Digestive (stomach) juice, lemon juice Battery acid Neutral [H + ] = [OH ] Increasingly Acidic [H + ] > [OH ] Increasingly Basic ] < [OH
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Buffers The internal pH of most living cells must remain close to pH 7 Buffers are substances that minimize changes in concentrations of H + and OH - in a solution Most buffers consist of an acid-base pair that reversibly combines with H +
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The Threat of Acid Precipitation Acid precipitation refers to rain, snow, or fog with a pH lower than 5.6 Acid precipitation is caused mainly by the mixing of different pollutants with water in the air Acid precipitation can damage life in lakes and streams Effects of acid precipitation on soil chemistry are contributing to the decline of some forests
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Chapter 4 Carbon and the Molecular Diversity of Life
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Overview: Carbon—The Backbone of Biological Molecules Although cells are 70–95% water, the rest consists mostly of carbon-based compounds Carbon is unparalleled in its ability to form large, complex, and diverse molecules Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds
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Concept 4.1: Organic chemistry is the study of carbon compounds Organic compounds range from simple molecules to colossal ones Most organic compounds contain hydrogen atoms in addition to carbon atoms Vitalism, the idea that organic compounds arise only in organisms, was disproved when chemists synthesized the compounds Mechanism is the view that all natural phenomena are governed by physical and chemical laws
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Concept 4.2: Carbon atoms can form diverse molecules by bonding to four other atoms In molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shape However, when two carbon atoms are joined by a double bond, the molecule has a flat shape
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LE 4-3 Molecular Formula Structural Formula Ball-and-Stick Model Space-Filling Model Methane Ethane Ethene (ethylene)
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Figure 4.5 Variations in carbon skeletons
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This note was uploaded on 03/30/2008 for the course BISC 221L taught by Professor Baudry,swanson during the Spring '08 term at USC.

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Lecture2 - Acids and Bases An acid is any substance that...

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