Understanding Equilibrium Constants 0 & 1

[ycn]

Hi, can someone help me on the following question.

Equilibrium constant=0

Equilibrium constant=1

What are the significance of these 2 values? As in, what is happening to the reactants as well as the products in this 2 instances? Thank you!

 

[Borek]

Write any reaction equation (even as simple as A <-> B), write expression for its equilibrium constant. Then it is simple math - think when equilibrium constant can equal 0 and when it can can equal 1, think in terms of values of concentrations of products and reactants.

 

[ycn]

But what do the numbers means?

Eg. a + b $$\Updownarrow$$ c + d

Kc = [c][d]/[a]

Kc = 1 will mean [c][d] = [a]

Kc = 0 will mean either [c] is zero or [d] is zero

1. Is the enthaply change for the reaction zero?
2. Is there no reaction?
3. Is the activation energy zero?

 

[Borek]

Let's start with the second case. If you start with a and b - what does it mean if c or d is zero? Think about the reaction stichiometry. If c is zero - what about d? How did a and b changed?

 

[ycn]

That means the other product should have zero concentration. Which also means no reaction would have taken place. Oh okok, thanks a lot, really!

Then in the case for Kc = 1, amount of reactant is equal to the product. That means half of the reactants have been converted into the product, and the reaction has just reached dynamic equilibrium. So can i say it's just a normal equilibrium reaction. Thanks

 

[Borek]

So can i say it's just a normal equilibrium reaction.

Sure you can, but it won't hurt to analyse it a little bit further. Think what it does mean when Kc > 1 or Kc < 1. Where the equilibrium lies - on the left, on the right? Kc = 1 doesn't have any special meaning, but it happens to be a border case.