# Equilibrium constant

Solution of these equations gives all the information needed to calculate the concentrations of all the species. Determination of equilibrium constants There are five main types of experimental data that are used for the determination of solution equilibrium constants. Potentiometric data obtained with a glass electrode are the most widely used with aqueous solutions. The experimental data will comprise a set of data points. Equilibrium Equilibrium constant Video transcript All of the reactions we've looked at so far have been of the form lowercase a moles of the molecule uppercase A, plus lowercase b moles of a molecule uppercase B.

They react to form the product or the products. Let's just say they have a couple of products. I could have had as many molecules here as I wanted. Let's say c moles of the molecule C plus d moles of the molecule capital D.

And the idea here is that they went in one direction. And if we did a little energy diagram, just going off of the kinematics video we just did, if that's the reaction, or how the reaction progresses, you could imagine that here you have it at a higher energy state. You have lowercase a moles of capital A molecule, plus lowercase b moles of capital B molecule, and you have some activation energy.

And then you get to a more stable state or a lower energy level here, where it's lowercase c moles of C molecule plus lowercase d moles of the D moles, and Equilibrium constant course, you had some activation energy. It only goes Equilibrium constant this direction. Once you get here, it's very hard to go back.

So that if you came Equilibrium constant and looked at this-- if you get enough of A and B-- you'll just be sitting with molecules of C and D. It'll only go in this direction. But that's not how it happens in reality. In reality-- well, it sometimes happens like this in reality where the reaction can only go in one direction.

But in a lot of cases, the reaction can actually go in both directions. So we could write, instead of this one-way reaction, we could write a two-way reaction like this. And not to confuse you too much, these are the number of moles or the ratios of the molecules I'm adding up, and they become relevant in a second.

So let's say I have lowercase a moles of this molecule plus lowercase b moles of this molecule, and then they react to form lowercase c moles of this molecule plus lowercase d moles of that molecule.

Sometimes the reaction can go in both directions. And to do that, to just show an equilibrium reaction, you do these arrows that go in both directions. That means that, hey, some of this is going to start forming into some of this. But at the same time, some of this might start forming into some of this. And at some point, I'm going to be reaching an equilibrium. When the rate of reaction of molecules going in that direction is equal to the number of molecules going in the other direction, then I'm going to reach some type of equilibrium.

Now, why would this happen as opposed to that? And I can think of one situation. If we draw this energy diagram again. Maybe both of these have similar or not so different energy states. There could be other reasons, but this is the one that comes to my mind.

Maybe the energy states look something like this. On this side, you have the A plus B, and then you need some activation energy. And then maybe the C plus D, maybe it's a little bit of a lower potential, but it's not that much lower.

So maybe they're favored to go in this direction, because this is a more stable state. So this is the A plus B, but here you have the C plus D. But it's not ridiculous to go this way either.

So most of it might go that way, but some of it might go this way. If some of these molecules just have the right amount of kinetic energy, they can surmount this activation energy and then go backwards to that side of it. And the study of this is called equilibrium, where you're looking at the concentrations of the different molecules.

And just to compare that to kinetics, kinetics was how fast is this is going to happen? Or what can I do to change the activation, this hump here?

Equilibrium is studying what will be the concentrations of the different molecules that end up, once the rate going in this direction is equal to the rate going in that direction.This example problem demonstrates how to find the equilibrium constant of a reaction from equilibrium concentrations of reactants and products..

Problem: For the reaction H 2 (g) + I 2 (g) ↔ 2 HI(g) At equilibrium, the concentrations are found to be [H 2] = M [I 2] = M [HI] = M What is the equilibrium constant of this reaction?. Solution. This mathematical relationship exists for all equilibrium systems, and produces a constant ratio called the equilibrium constant, K eq.

Note Equation is sometimes called the law of mass-action. Equilibrium chemistry is concerned with systems in chemical timberdesignmag.com unifying principle is that the free energy of a system at equilibrium is the minimum possible, so that the slope of the free energy with respect to the reaction coordinate is zero.

This principle, applied to mixtures at equilibrium provides a definition of an equilibrium constant. The equilibrium constant can help us understand whether the reaction tends to have a higher concentration of products or reactants at equilibrium. We can also use K c K_\text c K c to determine if the reaction is already at equilibrium.

UNChem Glossary. Click on the first letter of the term. [][][][][][f][][][][j][][][][][][][][][][][u][][][x][y][z]UNChem Main Page or Shodor Home Page. A acceleration. Oct 31,  · Calculating Kp or Kc - The Equilibrium Constant Given The Equilibrium Concentrations of The Reactants and Products 3.

Ice Table Problems - Determining Kc Given Equilibrium .

Reactions in equilibrium (video) | Khan Academy