Chemical Equilibrium of Reaction's constant?

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Discussion Overview

The discussion revolves around understanding the concept of equilibrium constants in chemical reactions, specifically how to determine which direction (forward or reverse) is favored based on the values of the equilibrium constants (Kc). Participants are exploring the implications of different Kc values and seeking clarity on the underlying principles.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about determining the favorability of forward versus reverse reactions based on given equilibrium constants (Kc=103, Kc=1, Kc=10-4).
  • Another participant states that the equilibrium constant is the ratio of the kinetic rate constants for the forward and reverse reactions.
  • A participant suggests that a high K value indicates that the forward reaction is favored, while a low K value suggests that the reverse reaction is favored.
  • There is a request for algebraic reasoning behind why a high K favors the forward reaction and a low K favors the reverse reaction.
  • A participant poses a question about the implications of K being greater than or less than 1 in terms of which substance is in excess and where the equilibrium lies.
  • Another participant provides a kinetic expression at equilibrium and suggests solving for the equilibrium constant algebraically.

Areas of Agreement / Disagreement

Participants generally agree on the relationship between the value of K and the favorability of the forward or reverse reactions, but there is uncertainty regarding the algebraic reasoning behind this relationship. The discussion remains unresolved regarding the specific calculations and interpretations of K values.

Contextual Notes

Participants have not fully resolved the mathematical steps or reasoning behind the favorability of reactions based on K values. There are also varying levels of understanding regarding the implications of K being greater than or less than 1.

Matriculator
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I'm currently studying for a test and I'm having problem with this concept:

If I have 3 different Equilibrium constants for different reactions like Kc=103, Kc=1 and KC=10-4, which one's forward reaction is most favorable, and which one's reverse reaction is most favorable?

Maybe it's the way the question is stated but I have a good understanding of most of the things in this chapter, this one doesn't make sense at all. Can anyone please help? Thank you very much.
 
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Matriculator said:
I'm currently studying for a test and I'm having problem with this concept:

If I have 3 different Equilibrium constants for different reactions like Kc=103, Kc=1 and KC=10-4, which one's forward reaction is most favorable, and which one's reverse reaction is most favorable?

Maybe it's the way the question is stated but I have a good understanding of most of the things in this chapter, this one doesn't make sense at all. Can anyone please help? Thank you very much.

The equilibrium constant is the ratio of the kinetic rate constant for the forward reaction to the kinetic rate constant for the reverse reaction.
 
Chestermiller said:
The equilibrium constant is the ratio of the kinetic rate constant for the forward reaction to the kinetic rate constant for the reverse reaction.

Thank you for replying. I understand that part, but what I'm having a hard time with is how to determine from different constants which movement(forward or backward) will be favorable(or not so).
 
Matriculator said:
Thank you for replying. I understand that part, but what I'm having a hard time with is how to determine from different constants which movement(forward or backward) will be favorable(or not so).
If K is high, then the forward reaction is favored over the reverse reaction. If K is low, then the reverse reaction is favored over the forward reaction.
 
Chestermiller said:
If K is high, then the forward reaction is favored over the reverse reaction. If K is low, then the reverse reaction is favored over the forward reaction.

But why is this so- perhaps algebraically? My teacher told me something like this but I couldn't make out the reasoning behind it. Thank you.
 
Write the equilibrium constant for the reaction

A -> B

If it is higher than 1 - which substance is in the excess? Where does the equilibrium lie, on the left, or on the right?

And if it is lower than 1?
 
For the reaction that Borek wrote, the kinetic expression at equilibrium is:

kf[A]-kr=0

Now solve algebraically for the equilibrium constant /[A]. This should be in your textbook.

Chet
 

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