Main_ISM_ch06 - Chapter 6: Chemical Equilibrium Problem...

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6-1 Chapter 6: Chemical Equilibrium Problem numbers in italics indicate that the solution is included in the Student’s Solutions Manual. Questions on Concepts Q6.1) Under what conditions is 0 dA a condition that defines the spontaneity of a process? This is the case at constant T and V if no nonexpansion work is possible. Q6.2) Under what conditions is 0 dG a condition that defines the spontaneity of a process? This is the case at constant T and P if no nonexpansion work is possible. Q6.3) Which thermodynamic state function gives a measure of the maximum electric work that can be carried out in a fuel cell? Δ G because nonexpansion dG dw ≤/ Q6.4) By invoking the pressure dependence of the chemical potential, show that if a valve separating a vessel of pure A from a vessel containing a mixture of A and B is opened, mixing will occur. Both A and B are ideal gases, and the initial pressure in both vessels is 1 bar. The chemical potential of A is lower in the mixture than in the pure gas because () ( ) ,l n A AA P TP T RT P μμ =+ o o , and P A < P º. Because mass flows from regions of high chemical potential to regions of low chemical potential, pure A will flow into the mixture, and the contents of both vessels will be mixed. Q6.5) Under what condition is K P = K x ? This is the case for a reaction involving gases if Δ n = 0. Q6.6) It is found that K P is independent of T for a particular chemical reaction. What does this tell you about the reaction? This is true if Δ H reaction = 0.
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Chapter 6/Chemical Equilibrium 6-2 Q6.7) The reaction A + B C + D is at equilibrium for ξ = 0.1. What does this tell you about the variation of G pure with ξ ? It tells you that f G Δ o for A + B is less than that for C + D. If the f G Δ o of reactants and products were nearly the same, would be near 0.5. If the f G Δ o for the products were less than those for the reactants, would be near 1. Q6.8) The reaction A + B C + D is at equilibrium for = 0.5. What does this tell you about the variation of G pure with ? It tells you that f G Δ o for A + B is equal to that for C + D. If the f G Δ o for the products were less than those for the reactants, would be near 1. If the f G Δ o for the reactants were less than those for the products, would be much smaller than 0.5. Q6.9) Why is it reasonable to set the chemical potential of a pure liquid or solid substance equal to its standard state chemical potential at that temperature independent of the pressure in considering chemical equilibrium? The pressure dependence of G for solids and liquids is very small, because the volume of liquids and solids changes very little unless very high pressures are applied. Therefore, it is a good approximation to set the chemical potential of a pure liquid or solid substance equal to its standard state chemical potential at the temperature of interest.
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This note was uploaded on 01/08/2010 for the course CHM 4411 taught by Professor Ohrn during the Fall '08 term at University of Florida.

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Main_ISM_ch06 - Chapter 6: Chemical Equilibrium Problem...

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