# Chemical Equilibrium of Reaction's constant?

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.

Chestermiller
Mentor
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.

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).

Chestermiller
Mentor
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.

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.

Borek
Mentor
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?

Chestermiller
Mentor
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