Lecture 1.
The equation of state Divide the world in two parts: the system and the environment (the medium). The system is in equilibrium with its environment (properties of the system and the medium
Chemical equilibrium continued We have derived the general relationship describing chemical equilibrium for any chemical reaction:
x = exp(G /RT) = K
i
i
0
where K is equ
Reversible first order reactions Although some processes can be approximately viewed as being irreversible, strictly speaking, there is no such thing as an irreversible react
The principle of detailed balance For the reaction A=B in equilibrium we have k1[A] = k1[B] or [B]/[A] = k1/k1 = KAB, where KAB is the equilibrium constant. Imagi
The temperature dependence of the rate constant For most chemical reactions, the temperature dependence of the rate constant is given by the Arrhenius law: k(T) = a Tn
Diffusion A molecule in a gas or a liquid frequently collides with other molecules and, as a result, its trajectory looks like a random walk. Here we will derive some p
Superheated and supercooled materials (continued from the last lecture). In the last lecture we have explained why gases can be supercooled below their condensation point: it
Thermodynamics of mixtures continued For a mixture, we have learned: dG = VdP-SdT + and G(P, T, n1, n2, ) =
dn
i
i
n
ii
where i ( P, T , n1, n2 , .) is the chemical potential of a component in the m
The Boltzmann distribution: the probability to have an energy i is given by:
pi i exp( i / kBT )
Examples of this 1. A piece of chalk on the table has the probability t
Phase equilibrium involving mixtures
Suppose we mix two liquids. What is the composition of the vapor that is in equilibrium with the liquid mixture? What is the boiling point
Protein folding
k A B k B A
d[ A] / dt = kA B [ A] + k B A [ B] d[ B] / dt = k A B [ A] kB A [ B]
A
B
Drive system out of equilibrium by rapid mixing, T-jump etc.
Signal, e.g.~[A]
~ exp ( k A B + k B
More examples of using thermochemistry
Example 1.
Calculate H and S for the process applied to one mole of water at P = 1 atm:
H2O(s, -10C) H2O(l, +10C)
CH353 Final Review
1) The Carnot cycle is a theoretical example of a perfect engine consisting of 4 steps:
i. Reversible isothermal expansion from state A to B at a hot temperature (Th)
ii. Reversible
CH353 Physical Chemistry I, Spring 2016
Thermodynamics, Statistical Mechanics, Chemical Equilibria
2/15/16 Lecture Summary
In last Fridays lecture, I introduced a new state function, called entropy, t
CH353 Physical Chemistry I, Spring 2016
Thermodynamics, Statistical Mechanics, & Chemical Equilibria
2/8/16 Lecture Summary
At the beginning of todays lecture, I continued our discussion of thermochem
Chemical equilibrium continued: the general approach
Extent of reaction
First of all, we will write any chemical reaction in the following general form:
A = 0
i i i
Here i
Chemical equilibrium
A chemical reaction reactants = products can go from left to right or from right to left. Many reactions however have a preferred direction: It is e
Lecture 3.
Going from one state to another (thermodynamic transformations). In thermodynamics, we will be generally interested in how the system behaves when it goes from one state to another. This qu
Work (path dependent quantities and functions of state) From physics you know that mechanical work = force displacement
Consider gas in equilibrium with the weight of the piston F. Now consider a proc
The 1st Law of thermodynamics q + W = dU U is a function of state (while q or W are not). U is called energy (or internal energy) of the system. If q = 0 this
What conditions should a process satisfy to be reversible? Are there any reversible processes to begin with?
To find out, consider the following example: a vertical cylinder covered with
The 2nd Law For any equilibrium (= reversible) process the quantity dS = q/T is an exact differential (i.e. an increment of a function of state). In other words
More examples of the 2nd law: 2nd law and heat engines: It is impossible to take heat q from a reservoir, convert it all into work, and return into the original state (
The microscopic origins of irreversibility and entropy in statistical mechanics For more on this issue, see the video of Feynmans lecture The Distinction Between Past and Fut
In the previous lecture we have introduced the Boltzmann formula for the entropy:
S = kB ln
Examples of using this: Example 1. (see previous lecture). Irreversible gas
The Gibbs free energy and nonPV work So far in our discussion of the work we have assumed it is associated with the expansion or compression of some material, in which c
Relating thermodynamic quantities A,G,H,U,S to measurable quantities (equation of state and heat capacities) If A(V,T) or G(P,T) is known for some material , all of its other
An example of using our general relationships for U(V,T), S(V,T) etc. : Entropy of a nonideal gas. Consider irreversible expansion of one mole of a gas, in which it occupi
Thermochemistry Many chemical reactions are accompanied by heat release. In others, the chemicals tend to get colder so one has to provide heat to maintain the temperature.