Energy: Conservation and Interconversion
The topic of energy has become a central focus of the entire globe. Issues of production, availability, and environmental impacts are all under active discussion: Consider the following items that have appeared i
Integrated Rate Laws
We observed the time dependences of zero, first, and second-order kinetics and saw the half-life relations that occur in such systems. Now, we would like to develop integrated (rather than differential rate law expressions. Heres w
So far, our discussion of chemistry has been concerned with the properties of initial and final states. Calculating equilibrium constants, for example, requires us to know information about the difference in energies of the reactants
Factors affecting equilibrium
We learned last time that
Thus, Keq = e
= e-(H - TS)/RT = e-H/RT e+S/R
We can define the enthalpic and entropic factors of the equilibrium constant as Enthalpic factor = and the entropic factor is given as
The Gibbs Free Energy
We have seen that the entropy, S, is a thermodynamic function of state that allows us to predict when a process is spontaneous or not. The entropy was invented as a variable that allows us to make this determination. Suniverse = S
So, now lets consider the reversible isothermal expansion of an ideal gas.
Pgas Pext Let the volume double in this expansion.
E = qrev + wrev = 0, so qrev = -wrev = +RT ln (Vf/Vi) Now, lets define S = qrev/T, so S = +R ln (Vf/Vi). ] In this partic
A few parting thoughts on thermochemistry
On thermochemistry: The enthalpies of formation of the elements in their standard states are zero. On carbon-based fuels: the problem with combustion of fossil fuels comes CO2 production. CO2 can be removed fro
A few comments on calorimetry
We always need to think about how heat is defined in a calorimetry experiment. We never just blithely write down Q = nCT and make the problem fit the formula. Lets consider two kinds of calorimetry problems: 1. Heat transf
In a laboratory calorimeter, combustion is often carried out. The T is measured, and the heat evolved when M grams of substance undergoes combustion is calculated from the heat capacity of the calorimeter and its contents. Note that the units are J per
Lets consider a simple example of the work done on the system (considered to be a gas) when a constant external pressure is applied to it.
Work done on the system = -(external force displacement) External force = external pressure s
Reaction Coordinates, Activation Energies, and Catalysis
So far, our discussion of kinetics has focused on the significance of the concentration terms in the rate laws. Now, we need to focus on what the rate constant means in terms of the energetics of