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Chemical Thermodynamics And the Thermodynamic Foundations of Life

Chemical Thermodynamics And the Thermodynamic Foundations of Life. Engines. capitalize on the fact that heat flows from hot to cold convert some heat to work. not all energy can be converted to work, some heat is always lost A cyclic process Takes you back to same P, T, U  U = Q - W = 0

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Chemical Thermodynamics And the Thermodynamic Foundations of Life

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  1. Chemical Thermodynamics And the Thermodynamic Foundations of Life

  2. Engines capitalize on the fact that heat flows from hot to cold convert some heat to work. • not all energy can be converted to work, some heat is always lost • A cyclic process • Takes you back to same P, T, U • U = Q - W = 0 • Q = W • Here, Q = QC + QH • Efficiency e = W / QH

  3. Same as U How much energy is available for work? “Free energy” Gibbs free energy G First law of thermo dE = dQ - dW adding in entropy and P-V work dE = T dS - P dV Define Gibbs free energy G = E + PV - TS a derivative & some algebra dG = V dP - S dT

  4. At equilibrium, P and T stay constant. Therefore, what is dG? dG = 0 (now think min, max, slope, entropy) dG = V dP - S dT G does the opposite of what entropy does: G is minimized

  5. Chemistry! G = how much useful work can be done (not just heat released) at constant T and P. At equilibrium, no more work can be done. We can think of a cell as an engine… dG = V dP - S dT +  dN

  6.  = chemical potential = how G depends on N (# molecules)  dN = the sum of all  dN for all chemical species involved in a reaction Example: N2 + 3 H2 --> 2 NH3 .  dN = 1 N2 + 3 H2 - 2 NH3 At equilibrium, G is at a minimum, so  dN = 0

  7. Experimental: Rate constant k: Chemical reactions proceed in a certain direction depending on T and P. How does it “know” which way to go? Rate = forward - reverse reaction rates

  8. A catalyst lowers the activation energy

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