Equilibrium-+Dynamic,+Chemical,+Physical+Equilibrium;+Le+Chatelier's+Principle;+Equilibrium+Constants

Introduction to Equilibrium

[|Equilibrium] is the state of a solution when the rate of the forward reaction is the same as that of the reverse reaction. There are several types of equilibrium, including: · [|Dynamic Equilibrium]- when the rates of the forward and reverse reactions are equal. The system is dynamic because individual molecules react continuously · Physical Equilibrium- very similar to chemical equilibrium, physical equilibrium does not involve any change in chemical properties. · [|Chemical Equilibrium]- the state in which the chemical activities or concentrations of the reactants and products have no net change over time
 * //What is Equilibrium?//**

With equilibrium equations, it is possible to find the molarities of the substances within the isolated cell. In order to find the equilibrium constant, K, the molarities of the equation must be put into this equation: 
 * //How is equilibrium utilized in chemistry?//**

where [C] and [D] represent the molarities of the products, with l and m representing their coefficients, and [A] and [B] represent the molarities of the reactants, with j and k representing their coefficients. These values are used to find equilibrium constants.

//**Iceboxes and Molarities**// ALSO, equilibrium constants can be used to find molarities within a cell. Equilibrium constants can usually be found in the back of a textbook, or are given in an equation when this is the case.

In order to find molarities, or find the concentration of H+ and OH- ions within a solution, the "icebox" method is used. The "icebox" method is a chart breaking down the process of equilibrium into 1) Initial Molarity, 2) Change in Molarity, and 3) End Molarity. This document explains and gives examples of how to do iceboxes: [|Iceboxes]

[|Some practice] with iceboxes.

__**EVEN MORE practice:**__ An equilibrium mixture of SO3, SO2, and O2 at 1000 K contains the gases at the following concentrations: [SO3] = 0.41 M, [SO2] = 0.032 M, and [O2] = 0.59 M. What is the equilibrium constant for the decomposition of SO3? 2 SO3(g) <==>2 SO2(g) + O2(g)

Answer: K= __[0.032]^2[0.59]__ [0.41]^2 K= 3.59 x 10^ -4


 * //What are the guidelines and tips for equilibrium expressions?//**
 * Solids and liquids are not included within expressions
 * The [|equilibrium constant] of the reverse reaction (K-1) is equal the inverse of the constant of the forward reaction (K)
 * equilibrium constants are usually found in the back of a textbook.
 * When a substance appears in a quantity higher than one mole, it is raised to the exponential power of the same value as its coefficient.
 * In order to find the equilibrium constant of an equation which had more than two parts, find the product of the equilibrium constants of each step. This represents the overall equilibrium constant for the equation.
 * K is most usually not given with units.
 * The value of K can indicate the ratio of products to reactants in equilibrium:
 * K > 1 indicates more products than reactants. This is because, within the equilibrium equation, the dividend (the products) must be greater than the divisor (the reactants) in order to obtain a K higher than 1.
 * K≈ 1 shows that the amounts reactants and products are about equal.
 * K < 1 indicates more reactants than products. This is because, within the equilibrium equation, the dividend (the products) must be less than the divisor (the reactants) in order to obtain a K less than 1.

Equilibrium change and manipulation is explained in[| Le Chatelier’s Principle]. Le Chatelier’s Principle states that if there is an upset within the system at equilibrium, the equilibrium will shift in a certain direction to accommodate the upset.
 * //How can equilibrium be changed/ manipulated?//**

In the equation, A + B <--> C + D, if you increased the concentration of A, equilibrium will move so that the concentration of A decreases- by reacting it with B and turning it into C +D, therefore equilibrium moves to the right.

If, in the same equation, you decreased the concentration of A, equilibrium will move to the left which means the C and D will have to react to replace the A that was removed.

According to this principle, in a gaseous equation, the positions of equilibrium will move in such a way as to counteract the change, which means that equilibrium will move so that pressure is reduced again.

__**Some practice:**__ For the following equilibrium: N2 (g) + H2(g) Û NH3 (g) D H= -386 KJ/mole Predict the direction the equilibrium will shift if: a) N2 is added? b) H2 is removed? c) NH3 is added? d) NH3 is removed?

Solutions: a) right b) left c) left d) right

For more on Le Chatelier's Principle: [|Le Chatelier's Principle for High School Students] [|Le Chatlier's Principle at Purdue]

[|This site explains ALL there is to know about equilibrium] //**__Works Cited__**//

"Chemical Equilibrium." __Wikipedia, the free encyclopedia__. 18 Mar. 2009 .

"Dynamic Equilibrium." __Wikipedia, the free encyclopedia__. 18 Mar. 2009 .

D., Neil. __Barron's AP Chemistry 2008 (Barron's How to Prepare for the Ap Chemistry Advanced Placement Examination)__. Danbury: Barron's Educational Series, 2007."Equilibrium -." __Wikipedia, the free encyclopedia__. 18 Mar. 2009 .

"Equilibrium constant -." __Wikipedia, the free encyclopedia__. 18 Mar. 2009 .

"Equilibrium: Introduction." __COOL School - Online Educational Content Development for K-12__. 18 Mar. 2009 .

"Fundamentals of Chemistry." __GenChem main page__. 18 Mar. 2009 .

"Le Chatelier's principle -." __Wikipedia, the free encyclopedia__. 18 Mar. 2009 .

"Le Chatelier's Principle." __AUS-e-TUTE for astute science students__. 18 Mar. 2009 .

"Le Chatelier's Principle." __Purdue University College of Science Welcome__. 18 Mar. 2009 .

Review, Princeton. __Cracking the AP Chemistry Exam, 2008 Edition (College Test Prep)__. Princeton: Princeton Review, 2007.

__TeacherWeb - Websites for Teachers__. 18 Mar. 2009 .

Thorpe, Gary S. __Chemistry (Cliffs AP)__. New Jersey: Cliffs Notes, 2001.