Full Excitation of Molecular Vibration Modes

Click For Summary
SUMMARY

The discussion focuses on determining the number of fully excited vibrational modes of a molecule based on the relationship of Cp/R as a function of temperature. Key examples include the values of Cp/R for various gases such as monatomic gases, linear rotors like N2, O2, and CO2, and specific molecules like water, methane, and 1-propanol. The conversation highlights the differences in Cp/R values for rigid versus floppy molecules, emphasizing the importance of understanding molecular degrees of freedom in relation to vibrational excitation.

PREREQUISITES
  • Understanding of Cp/R and its significance in thermodynamics
  • Familiarity with molecular degrees of freedom
  • Knowledge of vibrational modes in molecular structures
  • Basic principles of gas behavior and molecular classification
NEXT STEPS
  • Research the calculation of Cp/R for various molecular types
  • Explore the concept of vibrational modes in polyatomic molecules
  • Study the differences in molecular rigidity and its effect on Cp/R
  • Learn about the relationship between temperature and molecular excitation states
USEFUL FOR

Chemists, thermodynamics students, and researchers interested in molecular behavior and vibrational analysis will benefit from this discussion.

VincentLaw
Messages
1
Reaction score
0

Homework Statement


Given the relationship Cp/R as a function of Temperature, approximate the number of fully excited vibration modes at a given temperature for a given molecule.

2. The attempt at a solution
I have looked through several textbooks and many web sites, but I can't find this type of problem discussed anywhere. vaguely similar problems I have found only assume given excitation states. It seems like a relatively obscure problem, but I assume there is a generic solution process.
 
Physics news on Phys.org
I assume you are talking about degree of freedom, the total ways in which the molecule can exhibit motion, seeing you mentioned Cp/R.

Anyway, can you give a sample molecule on which you would like to attempt this question on?
 
Let's think specifically about Cp/R

What is the value of Cp/R for a monatomic gas? is it the same for all monatomic gases?

Now what is it for a linear rotor? Is it the same for N2, O2, CO2?

What about I2 -- that value is a little bit different -- why?

What is the value of Cp/R for water? Methane? Could you tell whether SO2 was linear or bent by looking at Cp/R?

How and why does Cp/R differ for a really floppy molecule like 1-propanol and a really rigid molecule like benzene?

And if you can work your way through all of that you should have a really good idea about the relationship between Cp/R and "fully excited" vibrational modes.
 

Similar threads

Chemistry Finding the molecular formula of an unknown hydrocarbon
  • · Replies 4 ·
Replies
4
Views
3K
Chemistry Absorption of light by molecules and the reasons for this
  • · Replies 19 ·
Replies
19
Views
11K
Finding band origin of electronic transition and wavenumber of vibrational mode
  • · Replies 3 ·
Replies
3
Views
12K
Implementing “Ab initio” approach in molecular mechanics method
  • · Replies 4 ·
Replies
4
Views
2K
Molecular-level explanation of macroscopic phenomena: dissolving
  • · Replies 5 ·
Replies
5
Views
3K
How to Convert Between Joules and Kilojoules in Quantum Theory
  • · Replies 2 ·
Replies
2
Views
3K
Graduate Calculating noise of a transducer from molecular vibration
  • · Replies 2 ·
Replies
2
Views
1K
Chemistry Determine Weight Percent given molecular weight....
  • · Replies 4 ·
Replies
4
Views
4K
Chemistry Understanding the calculation of enthalpy of the formation of benzene
  • · Replies 3 ·
Replies
3
Views
3K
Chemistry Estimating number of amino acids with protein molecular mass
  • · Replies 1 ·
Replies
1
Views
3K