Chapter 2 Water weak acids bases and buffers Learning objectives Important topics are highlighted in red 1 Know the structure and properties of water Single oxygen covalently bonded to two hydrogen atoms 104 5 degrees between hydrogen atoms Properties 2 Understand what are hydrogen bonds and how are hydrogen bonds formed Dipole dipople attraction between molecules The slightly positive hydrogen of one water molecule is attracted to the slightly negative oxygen of another water molecule or another electronegative atom of another molecule 3 Know the properties of hydrogen bonds directional and saturable Know the bond energy of hydrogen bonds and covalent bonds Hydrogen bond energy 23 kJ mol Covalent bond O H 470 kJ mol 4 Understand the different kinds of noncovalent bonds among biomolecules Ionic interactions 86 kJ mol Van der Waals forces the chart is confusing Hydrogen bond 20 kJ mol Dipole dipole interaction 9 3 London dispersion forces 3 5 Understand the physical properties of amphipathic molecules and their significance in biology Amphipathic molecules are chemical compounds that have both polar and nonpolar regions giving them both hydrophilic water loving and lipophilic fat loving properties They are important in the formation of biological membranes and micelles They create a barrier so not all substances can enter exit the cell Amphipathic compounds form special structures in aqueous solutions 6 Understand what are the colligative properties of solutions Boiling point Freezing point Vapor pressure Osmotic pressure These all depend on the number of particles ions or molecules in the solution 7 Understand what is osmotic pressure and be able to calculate osmotic pressure using the van t Hoff equation the pressure that would have to be applied to a pure solvent to prevent it from passing into a given solution by osmosis often used to express the concentration of the solution Van t Hoff equation ic RT ic osmolarity R gas constant T temperature in K 8 Understand what is dialysis and what are hypertonic isotonic and hypotonic solutions the separation of particles in a liquid on the basis of differences in their ability to pass through a membrane Hypertonic solution high solute concentration Hypotonic solution low solute concentration Isotonic solution equal concentration 9 Understand the definition of pH and be able to calculation pH H and OH of solutions pH way to specify acidity or basicity of an aqueous solution pH log 1 H log H Idk the rest man 10 Understand the Br nsted acid and base theory and what are conjugate acid base pairs An acid is a proton donor a base is a proton acceptor The pair consists of two substances that differ only by the presence of a proton H 11 Understand the theoretical definition of dissociation constant Ka and pKa of weak acids uh 12 Be able to calculate pH of weak acids solutions using the Henderson Hasselbach equation 13 Understand what are buffers and be able to calculate pH of buffer solutions using the Henderson Hasselbach equation Know how to make buffer solutions Buffers are solution that tend to resist the changes in pH when small amount of acid or base are added to it A buffer system contains a weak acid proton donor and its conjugate base proton acceptor or a weak base with its conjugate acid See equation from 12 14 Know the buffer systems in cells and blood and understand how do they work Buffering in the cell the phosphate buffer system H2PO4 HPO42 H Buffering for blood the bicarbonate system H2CO3 H HCO3 Coming back to this one 16 Understand the titration curve of phosphoric acids and the experimental meaning of pKa1 pKa2 and pKa3
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