Download pH and Organic Chemistry: Effects of Acids, Bases, and Carbon Compounds - Prof. Louis B. B and more Study notes School management&administration in PDF only on Docsity! 26 January Effects of Changes in pH Concentrations of H+ and OH- are equal in pure water Adding certain solutes, called acids and bases, modifies the concentrations of H+ and OH- Biologists use something called the pH scale to describe whether a solution is acidic or basic (the opposite of acidic) 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 The pH Scale In any aqueous solution at 25° C the product of H+ and OH- is constant and can be written as [H+] [OH-] = 10-14 The pH of a solution is defined by the negative logarithm of H+ concentration, written as pH = -log [H+] For a neutral aqueous solution [H+] is 10-7 = -(-7) = 7 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 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+ Threats to Water Quality on Earth 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 and can fall at some distance from the source of pollutants Acid precipitation can damage life in lakes and streams Effects of acid precipitation on soil chemistry are contributing to the decline of some forests Overview: Carbon: The Backbone of Life 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 Concept 4.1: Organic chemistry is the study of carbon compounds Organic chemistry is the study of compounds that contain carbon Organic compounds range from simple molecules to colossal ones Most organic compounds contain hydrogen atoms in addition to carbon atoms The Formation of Bonds with Carbon With four valence electrons, carbon can form four covalent bonds with a variety of atoms This tetravalence makes large, complex molecules possible 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 Hydrocarbons Hydrocarbons are organic molecules consisting of only carbon and hydrogen Many organic molecules, such as fats, have hydrocarbon components Hydrocarbons can undergo reactions that release a large amount of energy
