Boltzmann Distribution (Chemistry/ Physics)

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SUMMARY

The discussion focuses on the application of the Boltzmann distribution in calculating molecular states and thermodynamic parameters for a hyperstoichiometric compound, Al3O, and protein unfolding. The Boltzmann equation, nj/ni = e^(-(Ej-Ei)/kT), is utilized to determine the number of molecules in the ground state at temperatures of 300K and 3000K. Additionally, the thermodynamic parameters ΔH, ΔS, and ΔCp are analyzed to assess protein unfolding at 300K, with the equation ΔG = ΔH - TΔS being central to the calculations. Participants express confusion over differing equations from lecture notes and textbooks, highlighting the need for clarity in thermodynamic relationships.

PREREQUISITES
  • Understanding of the Boltzmann distribution and its equations
  • Familiarity with thermodynamic parameters: ΔH, ΔS, and ΔCp
  • Basic knowledge of vibrational energy spacing in molecular compounds
  • Experience with calorimetry and protein unfolding processes
NEXT STEPS
  • Research the derivation and applications of the Boltzmann equation in statistical mechanics
  • Study the relationship between ΔS and ΔCp in thermodynamic systems
  • Explore advanced topics in calorimetry related to protein stability and unfolding
  • Learn about the implications of temperature on molecular energy states and distributions
USEFUL FOR

Chemistry students, physicists, biochemists, and researchers involved in thermodynamics and molecular modeling will benefit from this discussion.

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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