Boltzmann Distribution (Chemistry/ Physics)

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Discussion Overview

The discussion revolves around the application of the Boltzmann distribution in two specific contexts: determining the number of molecules in the ground state of a hyperstoichiometric compound at different temperatures and calculating the number of protein molecules unfolded based on calorimetric data. The scope includes theoretical and mathematical reasoning related to thermodynamics and statistical mechanics.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents two questions involving the Boltzmann equation and thermodynamic parameters, expressing confusion over different equations encountered in lecture notes and textbooks.
  • Another participant suggests that the Boltzmann equation requires consideration of all states and their relative probabilities, indicating that the participant's approach may be valid.
  • There is uncertainty regarding the application of ΔCp in the context of protein unfolding, with one participant encouraging exploration of the relationship between ΔS and ΔCp.
  • A later reply acknowledges the challenge of the second question, describing it as both fun and difficult.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confidence regarding the equations and concepts involved. There is no consensus on the correct approach to the problems presented, and multiple viewpoints on the application of the Boltzmann equation and thermodynamic parameters remain evident.

Contextual Notes

Participants note discrepancies between equations found in different sources, which may lead to confusion. The discussion also highlights the need for clarity on how to incorporate ΔCp into the calculations for protein unfolding.

Who May Find This Useful

This discussion may be useful for students and individuals interested in thermodynamics, statistical mechanics, and the application of the Boltzmann distribution in chemical and physical contexts.

Klestine
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Homework Statement


Okay i want to ask 2 questions.
Question 1
Hyperstoichiometric compound Al3O has a vibrational energy spacing of 3.08x 10^-21J
how many molecules are present in the ground state at 300k and 3000K

Question 2
Calirimetric data for protein unfolding yielded following thermodynamic parameters
Parameter
ΔH (Tr) 220kJ/mol
ΔS (Tr) 0.68 kJ/mol/K
ΔCp 2.5 kJ/mol/K
how many protein molecules unfolded at 300K

Homework Equations


For question 1
Shown below is the Boltzmann equation
nj/ni = e-(Ej-Ei)/KT

Grond state equation is
nj/n0 = e-(Ej)/KT (this I found in a textbook)

For question 2

ΔG=ΔH-TΔS

The Attempt at a Solution



Okay for question the equation given in lecture notes is different to the equation i found in textbooks and the internet and it is

n0 = n(1-e-(ΔE)/KT

Two equations are confusing me, the this is if i use the equation given under relevant equations I get a weird answer,obviously wrong. Using the equation given in lecture notes it is easy and straight forward, but i doubt if it correct!

and for question 2 i have no clue what so ever to be honest. I do not know how i can use ΔCp

Thank you very much in advance for your help

Homework Statement


Homework Equations


The Attempt at a Solution


Homework Statement


Homework Equations


The Attempt at a Solution

 
Last edited:
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With the Boltzmann equation, you would have to consider all states (and add their relative probabilities), as this just gives a relative probability. Your equation at (3.) did take this into account, you can use it.

Question 2: No idea.
 
Klestine said:

Homework Statement


Okay i want to ask 2 questions.
Question 1
Hyperstoichiometric compound Al3O has a vibrational energy spacing of 3.08x 10^-21J
how many molecules are present in the ground state at 300k and 3000K

Question 2
Calorimetric data for protein unfolding yielded following thermodynamic parameters
Parameter
ΔH (Tr) 220kJ/mol
ΔS (Tr) 0.68 kJ/mol/K
ΔCp 2.5 kJ/mol/K
how many protein molecules unfolded at 300K

Homework Equations


For question 1
Shown below is the Boltzmann equation
nj/ni = e-(Ej-Ei)/KT

Grond state equation is
nj/n0 = e-(Ej)/KT (this I found in a textbook)

For question 2

ΔG=ΔH-TΔS


The Attempt at a Solution



Okay for question the equation given in lecture notes is different to the equation i found in textbooks and the internet and it is

n0 = n(1-e-(ΔE)/KT

Two equations are confusing me, the this is if i use the equation given under relevant equations I get a weird answer,obviously wrong. Using the equation given in lecture notes it is easy and straight forward, but i doubt if it correct!

and for question 2 i have no clue what so ever to be honest. I do not know how i can use ΔCp

Thank you very much in advance for your help
Question 2 looks like fun! :biggrin:

Think about what the link between ΔS and CP (\Delta S = nC_p ln\frac{T}{T_0}) means for the system.
 
thanx guys, question 2 is fun and an absolute killer
 

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