Chapter 9 Reaction Energetics
formation of the transition state of the reac
tion. The frequency of collisions between two
particles is expressed in terms of the product of their molar concentrations. The fraction of these collisions that yield the transition stat
e depends upon the activation energy of the
reaction, the thermal energy of the reacting molecules, and the orientation of the reacting molecules when they collide
.
Equilibrium is established when the products
and reactants reach the transition state at
the same rate. Solute concentrations and
gas pressures in an equilibrium mixture are
dictated by the equilibrium constant for the
reaction, K. The effect of adding or removing
reactants, products, or heat on the equilibrium
concentrations can be predicted by Le
Châtelier’s principle.
After studying the material presented in this chapter, you should be able to: 1. define the thermodynamic system, surroundings, and universe (Section 9.1); 2. state the first law of thermodynamics (Section 9.1); 3. determine
ΔE from q and w (Section 9.1);
- define enthalpy (Section 9.2); 5. define combustion and explai
n the importance of combustion reactions (Section 9.3);
- use bond dissociation energies to approx
imate enthalpies of reaction (Section 9.4);
- define entropy (Section 9.5); 8. predict the importance and the sign of
ΔS for a chemical reaction (Section 9.5);
- state the second law of thermodynamics (Section 9.6); 10.
define Gibbs free energy (Section 9.7);
11.
determine spontaneity from the sign of
ΔG (Section 9.7);
12.
determine the extent of
reaction from the sign of
ΔG
o (Section 9.8);
13.
discuss how the extent of reaction varies with T (Section 9.8);
14.
sketch a reaction energy diagram showing the activation energies for the forward and reverse reactions (Section 9.9);
15.
write the rate law for a simple collision process (Section 9.10);
16.
describe and define chemical equilibrium from
the viewpoint of kinetics (Section 9.11);
17.
predict
relative
rate constants and extents of reaction from reaction energy diagrams
(Section 9.11);
18.
explain the meaning of single versus double
arrows in a chemical equation (Section 9.11);
19.
write the equilibrium constant expressi
on for a chemical equation (Sections 9.11);
20.
predict the temperature dependence of
ΔG
o and K (Sections 9.8 and 9.11); and
21.
predict the impact of a stress
on an equilibrium (Section 9.12).
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