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lecture_3legge - Summary Equilibria, Molecules and Water...

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1 Equilibria, Molecules and Water Lecture 3 9/01/09 • Lecture 3 • Chapter 2 Voet, Voet and Pratt Summary Chapter 1 - Introduction to the Chemistry of Life 1. What can Biochemistry say about possible Origin of Life? 2. What are the possible advantages of Compartmentation of Cells? 3. How do Prokaryotes and Eukaryotes differ in levels of Organization? 4. How do we classify organisms? 5. Is there common ground for all cells? 6. How do the principles of Thermodynamics apply to living organisms? Equilibrium Constant K eq R = gas constant for a 1M solution Plot ln K eq vs. 1/T ( remember T is in absolute degrees Kelvin) ln K eq R H - o Δ = Slope R S o Δ T 1 = Intercept Van’t Hoff plot Standard State for Biochemistry Unit Activity 25 o C pH = 7.0 (not 0, as used in chemistry) [H 2 O] is taken as 1, however, if water is in the Keq equation then [H 2 O] = 55.5 eq K o G Δ G Δ The prime indicates Biochemical standard state For the reaction CH 3 COOH CH 3 COO - + H + , calculate Δ and Δ Gº’ (i.e. T = 25 ºC or 298K). The ionization constant for acetic acid is 1.8 x 10 -5 . Is this reaction spontaneous? 1. Δ Gº = -RT lnKeq = - (8.314J/mol/K) x (298K) ln(1.8 x 10 -5 ) = 27069 J/mol = 27kJ/mol 2. For Δ Gº’(the standard free energy change at pH7) Δ Gº’ = Δ Gº + RTln [CH 3 COO - ][H + ]/[CH 3 COOH] = 27069 + (8.314J/mol/K) x (298K) ln [10 -7 ] = 27069 - 39933 = -12864 J/mol Δ G = Δ G o + RTln [C] c [D] d [A] a [B] b Covalent bond The force holding two atoms together by the sharing of a pair of electrons. H + H H : H or H-H The force: Attraction between two positively charged nuclei and a pair of negatively charged electrons pair of negatively charged electrons. Orbital: a space where electrons move around. Electron can act as a wave, with a frequency, and putting a standing wave around a sphere yields only discrete areas by which the wave will be in phase all around. i.e different orbitals S and P
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2 Valence orbitals: outermost orbital that is filled or partially filled with electrons. These can overlap and form covalent bonds. Each orbital can have two electrons. Orbitals are designated by quantum numbers which define shells, orbital types spin etc electron or Val Max # 0f own val Bond Lone Element proton # orbital # electrons electrons # pairs H 1 1 2 1 1 0 C 6 4 8 4 4 0 N 7 4 8 5 3 1 O 8 4 8 6 2 2 Nitrogen N •Nitrogen has five valence electrons
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lecture_3legge - Summary Equilibria, Molecules and Water...

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