HelpMeWithPhChem

1. Physical Chemistry Help Page

Ask questions and look for answers here. The instructors will regularly check the page and answer questions, you should feel free to offer answers to your colleagues' questions as well.

1.1. How to ask a question

To keep the questions posted here tidy, please use the format below to pose a question, or to answer one

===== Put the question here. =====

The answer should follow

A sample...

===== What is the difference between Q and q? =====

Q refers to the partition function for the system, while q is the partition
 function for a single item in the system. In our applications, q is typicaly 
the molecular partition function.

1.2. Statistical Mechanics

1.2.1. General Questions

1.2.1.1. Which formulas are we expected to memorize?

It's useful to know the basic form of the partition function, beyond that, I will give them to you. Most of the formulas you will either use so often you will have a hard time forgetting them, or else will use so seldom, there is no point to memorizing them! mmf

1.2.1.2. What is the difference between Q and q?

Q refers to the partition function for the system, while q is the partition function for a single item in the system. In our applications, q is typicaly the molecular partition function. mmf

1.2.2. Chapter 17

1.2.2.1. Can we assume that Ei and Ej in problem 17-4 are in the same ensemble? That might be really great if we could!

Yes, the two E's are part of the same set! mmf

1.2.2.2. On page 696 of the textbook eq 17-11, is the constant C

On page 696 of the McQuarrie Simon book, is the constant "C" in equation 17-11 unique to the energy state "j" or is it the same for every possible energy state in the system/ensemble? In other words, can I assume that for

^{(-BEj))/aj and C' = (e}

You can assume that C is the same. mmf

1.2.3. Chapter 18

1.2.3.1. In problem 18-37, the question asks whether nitrogen is in thermodynamic equillibrium respect to vibrational energy....what does this mean in normal english?

What they mean in English is use stat mech to compute the relative populations of the levels. Those relative populations are the thermodynamic equilibrium values. If expt matches, then the molecules are in thermodynamic equilibrium! mmf

1.3. Thermodynamics

1.3.1. General Questions

1.3.2. Chapter 19

1.3.3. Chapter 20

1.3.4. Chapter 21

1.3.5. Bomb Calorimetery Lab

1.3.5.1. Did you once state that the nutritional information listed by Dove as calories are actually units of kcal?

I may have

and it is true, a nutrional "calorie" is actually a kilocalorie. This bit of trivia is usually covered in general chem. If you read a package of Canadian chocolate they will avoid the confusion and give the energy content of the food in kJoules.