Chemical Thermodynamics And the Thermodynamic Foundations of Life

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 = Q C + Q H Efficiency e = W / Q H 1.capitalize on the fact that heat flows from hot to cold 2.convert some heat to work. Engines

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

At equilibrium, 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 P and T stay constant.

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 Chemistry!

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

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 Rate constant k: Experimental:

A catalyst lowers the activation energy