Degree of dissociation accurately defined

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Discussion Overview

The discussion revolves around the definition of the degree of dissociation in the context of weak electrolytes. Participants explore whether this value, denoted as alpha, should be considered at the start of dissociation or at equilibrium, and how it relates to the amount of solute present.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether the degree of dissociation (alpha) is defined at the start of dissociation with 1 mole of solute or at equilibrium.
  • Another participant asserts that the degree of dissociation is a fraction of the substance that dissociated and does not depend on the amount of substance dissolved.
  • Some participants reference Wikipedia's definition, seeking clarification on whether it refers to dissociated moles per 1 mole at equilibrium or at the start of dissociation.
  • There is a contention regarding the relevance of the amount of substance in calculating the degree of dissociation, with some arguing that the ratio does not require this reference.
  • One participant suggests that the degree of dissociation can be defined independently of equilibrium and can be measured over time after introducing the substance into a solvent.

Areas of Agreement / Disagreement

Participants express differing views on whether the degree of dissociation should be defined at the start of dissociation or at equilibrium, indicating that multiple competing views remain without consensus.

Contextual Notes

There are unresolved questions regarding the definitions and assumptions related to the degree of dissociation, particularly concerning the role of equilibrium and the amount of solute.

Entanglement
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Is the degree of dissociation the value of

Alpha when the dissociation begins with 1 mole of the solute, or is it alpha when the solute is 1 mole at equilibrium,
There isn't a difference since I'm talking about very weak electrolytes but I want to know the accurate answer.
 
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Degree of dissociation is a fraction of substance that dissociated, and it doesn't depend on the amount of substance dissolved.
 
Borek said:
Degree of dissociation is a fraction of substance that dissociated, and it doesn't depend on the amount of substance dissolved.
It's said on Wikipedia that is the value of dissociated moles per 1 mole,

It is meant one mole at equilibrium or when the dissociation begins with that 1 moles ?
 
I don't care about what wikipedia says. Degree of dissociation is a fraction of the substance that dissociated. You start with n moles, m moles dissociate, degree of dissociation is m/n.
 
Borek said:
I don't care about what wikipedia says. Degree of dissociation is a fraction of the substance that dissociated. You start with n moles, m moles dissociate, degree of dissociation is m/n.
Ok, m/n will give the value of m when n is 1, there's no contradiction
 
No contradiction, but a lousy thinking. Ratio doesn't require referring to the amount of substance.
 
Borek said:
No contradiction, but a lousy thinking. Ratio doesn't require referring to the amount of substance.
"n moles" is the number of moles at equilibrium or the number of moles that the dissociation starts with ?
 
The degree of dissociation can be defined independently of equilibrium.
E.g., you could measure it as a function of time after bringing an undissociated substance into a solvent.
 
Borek said:
You start with n moles, m moles dissociate

ElmorshedyDr said:
"n moles" is the number of moles at equilibrium or the number of moles that the dissociation starts with ?

Perhaps it is time you start paying attention to what you read.
 
  • #10
Borek said:
Perhaps it is time you start paying attention to what you read.
I'm sorry, thanks a lot for you help
 
  • #11
I have a question about the ionic product of water

How is Kw = [ H ] [ OH ] = 10^-14 mole/ liter derived.
 
  • #12
It is not derived, it is determined experimentally.

Please start new threads for new questions.
 

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