chapter14

 Chapter 14: Chemical Equilibrium  toc [|Online Tutorial] [|Sliding through the info]

=**Some Basics **=
 * A + B => C + D (forward reaction)
 * C + D => A + B (reverse reaction)
 * Initially there is only A and B so only the forward reaction is possible
 * As C and D build up, the reveres reactions speeds up while the forward reaction slows down.
 * Eventually the rates become equal.

= **The Concept of Equilibrium and the Equilibrium Constant ** =  //__ The Equilibrium Constant __//
 * Most chemical reactions are reversible to some extent.
 * As soon as some product molecules are formed, the reverse process begins to take place and reactant molecules are formed from product molecules
 * Chemical equilibrium - achieved when the rate of the forward and reverse reactions are equal and he concentrations for the reactants and products remain constant.
 * Physical equilibrium - the changes that occur are physical processes
 * Double arrows (<=> means reaction is reversible)
 *  Gas concentrations are expressed in morality, which can be calculated from the number of moles of the gases present initially and at equilibrium and volume of the flask in liters
 *  Where K is a constant for the equilibrium reaction [[image:3.jpg]], then[[image:4.jpg]] which is also known as the equilibrium constant.
 *  Law of mass action - for a reversible reaction at equilibrium and a constant temperature, a certain ratio of reactant and product concentrations as a constant value, K (equilibrium constant)
 *  The equilibrium constant is defined by a quotient, the numerator is obtained by multiplying together the equilibrium concentrations of the products and then each is raised to a power equal to the stoichiometric coefficient in the balanced equation
 *  The denominator is obtained by multiplying the equilibrium concentrations of the reactant and raising each to the power that is equal to the coefficient.
 *  Magnitude of equilibrium constant tells whether an equilibrium reactions favors the products or the reactants
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> If K is much greater than 1, the equilibrium will favor the right, also known as the products
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> If K is much smaller than 1, the equilibrium will favor the left, also known as the reactants.

= **<span style="color: rgb(0, 128, 0); font-family: 'Times New Roman',Times,serif;">Writing Equilibrium Constant Expressions ** = <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> //__ Homogeneous Equilibria __// (http://www.tvgreen.com/apchapt13/apchapt13_files/frame.htm) (<span style="color: rgb(0, 0, 0);">Zumdahl, 4th Edition. )
 * There are many ways to express the concentrations of reactants and products because they are not always in the same phase
 * It is also a general rule of thumb to not use units for the equilibrium constant
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Homogeneous equilibrium - reactions in which all reacting species are in the same phase
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Kp tells that equilibrium concentrations are expressed in terms of pressure
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Usually Kp is not equal to Kc because partial pressures of reactions and products are not equal to their concentrations expressed in moles per liter.

<span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> //__ Heterogeneous Equilibria __// (http://www.tvgreen.com/apchapt13/apchapt13_files/frame.htm)
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Heterogeneous equilibrium - reversible reaction involving reactants and products that are in different phases.
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Basically, the products and reactants are in different states of matter.
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> “Concentration” of a solid is an intensive property and does not depend on how much of the substance is present so when writing your equilibrium equation it is not necessary to include solids.
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Liquids also are not included in equilibrium equations.

<span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> //__ Multiple Equilibria __// (Chang, 8th edition)
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Product molecules in one equilibrium system are involved in a second equilibrium process
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> If a reaction can be expressed as the sum of two or more reactions, the Equilibrium constant for the overall reaction is given by the product of the equilibrium constants of the individual reactions
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> An example would be the ionization of diprotic acids in aqueous solution.

<span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> //__The Form of K and the Equilibrium Equation__// (Chang, 8th edition)
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> There are two important rules for writing equilibrium constants
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> 1. When the equation for a reversible reaction is written in the opposite direction, the equilibrium constant becomes the reciprocal of the original equilibrium constant.
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> 2. The value of K also depends on how the equilibrium equation is balanced.

= **<span style="color: rgb(0, 0, 255); font-family: 'Times New Roman',Times,serif;">The Relationship between Chemical Kinetics and Chemical Equilibrium ** = <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> //__Predicting the Direction of a Reaction__//
 * The equilibrium constant helps us to predict the direction in which a reaction mixture will proceed to achieve equilibrium and to calculate the concentrations of reactant and products once equilibrium has been reached
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Reaction quotient (Qc)- for reactions that have not reached equilibrium, instead of the equilibrium constant by substituting he initial concentrations into the equilibrium constant expression
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> We compare the values of Qc and Kc to determine the direction in which the net reaction will achieve equilibrium
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Qc < Kc : ratio of products to reactant is too small. To reach equilibrium reactants must be converted to products. System proceeds from left to right to reach equilibrium
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Qc = Kc : The concentrations are equilibrium concentrations. The system is at equilibrium
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Qc > Kc : Ratio of concentration is too large. To reach equilibrium, products must be converted to reactants. System proceeds from right to left to reach equilibrium.

= **<span style="color: rgb(166, 34, 206); font-family: 'Times New Roman',Times,serif;">Factors That Affect Chemical Equilibrium ** = <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> __ Le Chatelier’s Principle __ <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> __ Changes in Concentration __ <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> __ Changes in Volume and Pressure __ <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> __ Changes in Temperature __ <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> __ The Effect of Catalyst __ <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> __ Summary of the Factors That May Affect the Equilibrium Positions __
 * Changes in experimental conditions may disturb the balance and shift the equilibrium positions so that more or less of the desired products is formed.
 * If it shifts to the right, the net reaction is now from left to right
 * Variables that can be controlled experimentally are concentration, pressure, volume, and temperature
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Helps predict the direction in which an equilibrium reaction will move when a change in concentration, pressure, volume, or temperature occurs
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Le Chatelier’s principle- if an external stress is applied to a system at equilibrium, the system adjusts in such a way that the stress is partially offset as the system reaches a new equilibrium position
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> “stress” means a change in concentrations, pressure, volume, or temperature that removes the system from the equilibrium state.
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> We use Le Chatelier’s principle to assess the effects of the changes
 * All reactants and products are present in the reacting system at equilibrium
 * Increasing the concentrations of the prod cuts shifts the equilibrium to the left, and decreasing the concentration of the products shifts the equilibrium to the right
 * The change in equilibrium is predicted by Le Chatelier's principle
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Usually, changes in pressure do not affect the concentrations of reacting species in condensed phases because gas and liquids are pretty much impressible
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Gases are greatly affected by changes in pressure though
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> PV=nRT and P= (n/V) RT
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> P and V are related inversely (greater the pressure, smaller the volume, and vice versa)
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Term (n/v) is the concentration of the gas in mol/L (varies directly )
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> An increase in pressure (decrease in volume) favors the net reaction that decreases the total number of moles of gases (the reverse reaction)
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> decrease in pressure (increase in volume) favors the net reaction that increases the total number of moles of gases (the forward reaction)
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> For reactions where there is no change in the number of moles of gases, a pressure (or volume) change has no effect on the position of equilibrium
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> It’s possible to change the pressure of a system without changing its volume
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> A change in concentration, pressure, or volume does not change the value of the equilibrium constant
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Only a change in temperature can alter the equilibrium constant
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> At equilibrium at a certain temperature, the heat effect is zero because there is no net reaction
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> A rise in temperature “adds” heat to the system and a drop in temperature ‘removes” heat from the system
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Like any change in concentration, pressure, or volume, the system shifts to reduce the effect of the change
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Temperature increase= endothermic direction (left to right of the equilibrium equation)
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Temperature decrease = exothermic direction ( from right to left of the equilibrium equation
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> The equilibrium constant increases when the system is heated and decreases when the system Is cooled
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Catalysts enhance the rate of a reaction by lowering the reaction’s activation energy
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Catalysts lowers activation of the forward and reverse reactions to the same extent
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> THE PRESENCE OF A CATALYST DOES NOT ALTER THE EQUILIBRIUM CONSTANT OR SHIFT THE POSITION OF AN EQUILIBRIUM SYSTEM
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Adding a catalyst not at equilibrium will simply cause the mixture to reach equilibrium sooner
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> The same equilibrium mixture could be obtained without the catalyst, but might take longer
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Total of four ways to affect a reacting system at equilibrium
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Only a change in temperature changes the value of the equilibrium constant
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> Changes in concentration, pressure, and volume can alter the equilibrium concentrations of the reacting mixture, but cannot change the equilibrium constant
 * <span style="font-family: 'Times New Roman'; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"> A catalyst can speed up the process but has no effect on the equilibrium constant or on the equilibrium concentrations of the reacting species

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=<span style="color: rgb(255, 0, 145); font-size: 130%;">Extras <span style="color: rgb(114, 34, 206); font-size: 130%;"> = =<span style="color: rgb(114, 34, 206); font-size: 130%;"> = <span style="color: rgb(114, 34, 206); font-size: 130%;"> Here are problems of all different types that you have encountered in this chapter... (problems from Chang Chemistry, 8ed.)

<span style="color: rgb(255, 0, 145);">Now that you know all the background information, let's see it in action!!!!

<span style="color: rgb(255, 237, 0); font-family: 'Comic Sans MS',cursive; background-color: rgb(218, 174, 234);"> <span style="font-family: 'Comic Sans MS',cursive;">Some bonus info [|chemical stuff]

<span style="color: rgb(255, 255, 0); background-color: rgb(255, 0, 114); font-size: 185%; font-family: 'Comic Sans MS',cursive;">HOPE YOU NOW KNOW ALL ABOUT CHEMICAL EQUILIBRIUM =D

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Majority of the information came from Chang Chemistry, 8ed <span style="font-family: 'Comic Sans MS',cursive; color: rgb(255, 237, 0); background-color: rgb(218, 174, 234); font-size: 130%;">