How do we derive the equilibrium constant formula?

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Discussion Overview

The discussion focuses on the derivation of the equilibrium constant formula, specifically the expression for Kc in chemical reactions. Participants explore various aspects of the equilibrium constant, including its definition, examples, and different methods of derivation, touching on both basic and advanced concepts in chemistry.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant requests clarification on how to derive the equilibrium constant formula, specifically Kc.
  • Another participant explains that the equilibrium constant is calculated by taking the product of the concentrations of the products raised to their coefficients divided by the product of the concentrations of the reactants raised to their coefficients.
  • A specific example of a redox reaction is provided to illustrate how to write the equilibrium constant.
  • Some participants express a desire for a more detailed explanation involving physical chemistry concepts, such as chemical potentials.
  • Links to external resources are shared, which may provide further insights into the derivation of the equilibrium constant.
  • One participant notes that understanding the relationship between rate constants and the equilibrium constant is important for grasping the concept more deeply.
  • A participant admits to creating a redox example and questions its validity.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and interest in different methods of deriving the equilibrium constant. While some agree on the basic definition and formula, there is no consensus on the best approach to derive it, and multiple perspectives on the complexity of the topic are present.

Contextual Notes

Some participants indicate a lack of familiarity with advanced concepts in physical chemistry, which may limit their understanding of the derivation process. Additionally, there are references to external resources that may not be universally accessible or comprehensible to all participants.

Who May Find This Useful

This discussion may be useful for students and individuals interested in chemistry, particularly those seeking to understand the equilibrium constant and its derivation from both basic and advanced perspectives.

Cheman
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How do we derive the equilibrium constant formula?

ie: Kc= [C]^c*[D]^d/ [A]^a*^b

Thanks in advance. :smile:
 
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To start with basics: the product of concentrations of ionic species belonging to right side (products) over the product of concentrations of ionic species belonging to the left side (reagents)

Now let me give a real example:

[tex]5Fe^{2+}+MnO_4^-+8H^+\leftrightharpoons 5Fe^{3+}+Mn^{2+}+4H_2O[/tex]

The equilibrium constant may be written like this:

[tex]K_{redox}=\frac {[Fe^{3+}]^5\times [Mn^{2+}]}{[Fe^{2+}]^5\times [MnO_4^-] \times [H^+]^8}[/tex]
 
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The equilibrium constant Kc=[Products]^coeffcient/[Reactants]^coefficients

In words: The equilibrium constant is the concentration of the products raised to the power of the coefficient in front of them of the balanced equation divided by the concentration of all the reactants raised to their coefficients. This is of course the "easy" explanation of an equilibrium consant, you probably don't want to see the P-chem explanation.
 
Gravenewworld, my P-chem really sucks, would you please show it, so that I can learn how to do it by using P-chem?
 
http://www.sdsc.edu/chemdyn/classnotes/equil.html

I have no idea how to use Latex, so it would almost be impossible to write down how it is derived. That website shows how to derive the equilibrium constant for gases which will give you an idea of how it is derived in general. You have to work with chemical potentials etc. to derive the equilibrium constant.
 
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This site may also help http://www2.mcdaniel.edu/Chemistry/ch307.notes/Chemical%20Equilibrium.html
 
Wow, they are very good, even too good for me to nearly impossible to understand them easily :smile: However I will devote my energy to learn the basics in it. Thank you for your interest.
 
Your chemistry text should explain this in simple terms, the easiest way to understand equilibrium constant is in terms of the rate constants. The derivation from the forward and reverse rate constants should be given in your text. It is quite important that you understand the relationship between rate constants and equilibrium constatn.

It seems that they have explained the rest. although it is a bit more complex . You should study this section more in depth.

Chem tr. where did you get the redox example (your first post)?
 
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I have totally made up this one, but it doesn't seem to be wrong...
 

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