AP chem chemical Equilibrium
what phases are not effect by changes in pressure
aqueous solution BUT gases are greatly effect by pressure
pressure , volume and concentration do what to a reaction
can alter the equal lib concentration
what is the significant limitations in K 's use as a mesure
can only be determined during equilibrium
how does pressure effect equilibrium ? (Le Chatelier's Principle)
changes in pressure usually don't effect equilibrium in
variables that can effect an equilibrium are
concentration ,pressure , volume and temperature
the relationship between chemical kinetic and equilibrium
consider simple elementary step kf A + 2B ↔ kr the forward reaction rate f = Kf[A][B]² and reverse rate is given by rate r =Kr[AB₂] where Kf and Kr are the rate constant for the forward reaction and the reverse when no net changes occur , the two rate much be equal rate f = rate r basically Kc is always a constant regardless of the equilibrium concentration of the reacting species because it is always equal to kf/kr the quotient of the two quantities that are constant at a given temperature in conclusion we see in terms in chemical kinetics that the equilibrium constant of a reaction can be expressed as a ratio of rate constant of the forward and revise reaction.this analysis explains why the equilibrium constant is a constant and why value changes with the temperature
What is the relationship between Kp and Kc for the reaction, 2ICl(g) I2(g) + Cl2(g)? a) Kp = Kc(RT)-1 d) Kp = Kc b) Kp = Kc(RT) e) Kp = Kc(2RT) c) Kp = Kc(RT)2
d the answer!!1!!!!1!q
The effects of catalyst on equilibrium
does not effect equilibrium or the equilibrium constant
phases equilibrium
equilibrium between two phases because the changes that occur are physical changes
lower k equal = upper case K =
for kinetic equilibrium
multiple equilibria
for more complicated situations is one in which the product molecules in one equilibrium system are involved in a second equilibrium process A + B↔ C +D C + D ↔ E + F can write it as K'c=[C][D]/[A][B] K"=[E][F]/[C][D] overall reaction is A + B ↔ E + F the equilibrium constant is Kc = [E][F]/[A][B] we obtain the same expression if we take the product of the expression for K'c and K"c K'c and K"c= [C][D]/[A][B] X [E][F]/[C][D]=[E][F]/[A][B] therefore Kc = K'c Kc'' basically cross out same thing on opposite sides of the the two equation and multiple the two value
le Chatelier's principle
help us decide which way reaction will occur state that if an external stress is added to the system at equilibrium , the system adjusts in such a way that the stress is partially offset as the system reaches a new equilibrium. the word stress mean a change in concentration,temperature volume or pressure
k can tell us if equilibrium favors reactant or product
if k is much greater than 1 (K>>1) the equilibrium will lie to the right and the product is more favored reaction favors product if equilibrium constant is smaller than one (K << 1) than equilibrium will lie to the left and favor the reactants in this content any number greater than 10 is consider to be much greater than one any number less than 0.1 is consider much less than one
calculating equilibrium concentration
if we a equilibrium constant for a particular reaction we can calculate the concentration in the equilibrium mixture from intial concentration. commonly only the initial reactants concentration are given basically to solve for this value you know is that value minus x under x value have no information about then solve for X with know k then add value you got into x
rule of 100 for ice table problems how dio you check if your right
if your C/K is greater then 100 gwt rid of plus or mins just have x whatever C: concentration K:equil lib constant and it usually concentration underneth one give you
law of mass action
in chemistry, the law of mass action is the proposition that the rate of a chemical reaction is directly proportional to the product of the activities or concentrations of the reactants. It explains and predicts behaviors of solutions in dynamic equilibrium
An unsaturated solution is a chemical solution ....... really good one
in which the solute concentration is lower than its equilibrium solubility. All of the solute dissolves in the solvent.
As the temperature of the solvent increases, solubility .................
increases
Dynamic equilibrium-
indicates that the reaction is proceeding in the forward and in the reverse direction simultaneously and once equilibrium is established, the rate of each direction is equal. This also keeps the concentration of reactants and products constant (which is not to be confused with "equal").
chemical equilibrium
is achieved when the rate of the forward and reverse reaction are equal and the concentration of the reactant and product remain constant. chemical equilibrium is a dynamic process
reaction quotient
it is Q
adding catalyst does what to the reaction
makes it reach equilibrium sooner
for the kp at a certain temperature for the nΔ you use what formula ( not really a formula)
moles of gases product - moles of gases reactant
endothermic reaction and you increase temperature which way will reaction shift
move to the right move where there no heat or delta H !
the concentration of n/v* increase or decreases when volume decreases *basically meaning pressure i think
n/v increses
if moles are the same then equilibrium shifts ....
no change in shift if moles are equal :)
does pressure ,concentration volume effect the equilibrium constant K
no,temperature does though
if your doing ice problems and you have to do the quadratic formula and end up with two answer which two answer due you choses if you have a positive and a negative
positive one
Kp is for ...
pressure
if K is Greater than one ...
product are favor K>>1
thing need to know for equilibrium constant
product on top and reactant on the bottom the coefficients become exponents aA + bB↔cC + dD k=[C]^c[D]^d/[A]^a[B]^b
CHANGING STOICHIOMETRIC COEFFICIENTS when the stoichiometric coefficients of a balanced equation are multiplied by some factor, the K then ...
raised to the power of the multiplication factor (Kn). Thus, 2x is K squared; 3x is K cubed; etc.
if K>Q
reaction proceed forwards reactant convert to product right
if K < Q
reaction proceed in reverse direction product convert to reactents. left
when your reporting K you must....
report the temperature and write out the equation
heterogeneous Equilibria
result from a reversible reaction involving reactant and product that are in different phases
double arrow ( ↔ ) mean the reaction is ......
reversible
to show the equilibriumis favoring something YOU MUST DO what ?
show ⇌ both arrow the side the reaction is being favored the most is longer MUST have other arrow there to longer one on top
if both values are positive which when do you choses ice table problems
since hoave to plug in equation with x pick the one when you subtract that if you an positive value
omit any pure ....
solide or liquids
Precipitates form when the solution..........
supersaturated!!!
Q=k
system already at equilibrium
REVERSING EQUATIONS switch equation(fliping it)
take the reciprocal of K ( 1/K)
what effects constant K pressure ,concentration volume,temperature ?
temperature
k remain constant if bank is held constant
temperature and I THINK it is 25 ° C
Kc' means
that one of the species is held constant
Heterogeneous Equilibria
the position of a heterogeneous equilibrium does not depend on the amounts of pure solids or liquids present B. If pure solids or liquids are involved in a chemical reaction, their concentrations are not included in the equilibrium expression for the reaction C. Pure liquids are not the same as solutions, whose concentration can change 13.5 Applications of the Eq
for reaction that have not have reach equilibrium we obtain
the reaction quotient (Qc), instead of the equilibrium constant by substituting the initial concentration into the equilibrium constant expression to determine the direction in which the net reaction will proceed to achieve equilibrium we compare the values of Qc and Kc. the three possible cases are as follows Qc < Kc(product smaller than product) the ratio of the initial concentration of product to reactant is to small. To reach equilibrium reactant must be converted to product. the system proceed from left to right Qc=Kc the intial concentration are equilibrium concentrations. the system is at equilibrium Qc> Kc The ratio of initial concentration of product to reactant is to large ( to much product) to reach equilibrium product much be converted to reactant. the system must proceed from left to right (consuming product forming reactant) to reach equilibrium
decreses in pressure which side will the reaction move to
the side with more moles (total of moles)
increases pressure which side will reaction move to
the side with the least amount of moles
Q = Ksp
the system is at equil. (saturated)
a really good one for adding equilibrium together
to what ever which your thing reaction that will add a give you or cancel out what you needd. if you to reverse reaction do 1/k to get the answers verysimpler to hess's law except you don't o neg and positive like you did with heat and you don't add at end you multiply and if double reaction rise it to the power you myuilptlu the entire reaction by
if a reaction equation is double by 2 and you multiply the the coefficients by that what do you do with the K (constant)
what ever the number K^ ro the the power the what ever coefficient was multiplied
homogeneous equilibria
which all reacting species are in the same phase an example is the dissociation of of N2O4. the equilibrium constant , as given in equation Kc [N₂O]²/[N₂O₄] note : that the subscript c represent concentration of the reacting species are expired in molarity N₂O and N₂O₄ are both gases and can be express in terms of there partial pressure at a constant temperature the partial pressure is directly related to molarity thus P=(n/V)RT than... Kp=P² NO₂/P N₂O₄ WHERE PNO₂ AND P N₂O₄ are the equilibrium partial pressure (in atm) of the NO₂ and the N₂O₄ the subscript in Kp tells us that equilibrium concentration is express in pressure. in general Kp is not equal to Kc
is it possible to change of a system without changing the volume ? HOW
you can leave gases in same volume container but to change the pressure without changing the volume add a insert gas (ex: helium) adding helm increases pressure and decreases the mole pressure of gases BUT the partial pressure of each gas , given by the product of its mole fraction and the total pressure does not change thus the present of noble gases in equilibrium does not effect equilibrium.
At equilibrium at a certain temperature the heat effect is what number
zero because there is no reaction
ESTIMATING SALT SOLUBILITY FROM Ksp
Relative solubilities can be deduced by comparing values of Ksp BUT, BE CAREFUL! These comparisons can only be made for salts having the same ION:ION ratio. Please don't forget solubility changes with temperature! Some substances become less soluble in cold water while other increase in solubility! Aragonite is an example. Example: The Ksp for CaCO3 is 3.8 × 10−9 @ 25C. Calculate the solubility of calcium carbonate in pure water in (a) moles per liter & (b) grams per liter:
Soluble is often defined
"greater than 3 grams dissolving in 100 mL of water
ADDING EQUATIONS
(K1 × K2 × K3 ...)
summary of guidelines for writing for writing equilibrium constant expression
1) The concentration of the reacting species in condensed phase are expressed in mol/l; in the gaseous phase the concentration can be expressed in mol/l or in atm. Kc is related to Kp by a simple equation 2)the concentration of pure solid , pure liquid (in heterogeneous equilibrium) and solvents in ( homogenous equilibria) do not appear in the equilibrium constant expressions 3) the equilibrium constant (Kc or Kp) is a dimensionless quantity) (NO unites) 4) in quoting a value for the equilibrium constant, we must specify the balanced equation and the temperature. 5) if a reaction can be expressed as the sum of two or more reactions , the equilibrium constant for the overall reactions is given by the product of the equilibrium constants of individual reactions.
the form of K and the equilibrium equation two important rules when writing K
1)when the equation for a reversible reaction is written in opposite direction the equilibrium constant becomes the reciprocal of the original equilibrium example NO2-N2O4 N₂O₄(g) ↔ 2NO₂ (g) at 25c if revises can writ it as 2NO₂(g) ↔ N₂O₄(g) K'c=[N₂O₄]/[NO₂]² = 1/Kc = 1/4.63 X 10⁻³=216 you can see that Kc= 1/Kc' or KcKc = 1.00 2) the value of K also depends on how the equilibrium equation is balanced consider the following ways to describing the same equilibrium 1/2 N₂O₄↔NO₂ Kc'= [NO₂]/[N₂O₄]^1/2 N₂O₄ ↔2NO₂ Kc = [NO₂]²/[N₂O₄] looking at the exponents we see that Kc' = square root k there fore Kc= 4.63 X 10⁻³ therefore k'c= 0.0680 according to the law of mass action each concentration term in equilibrium is rated to a power equal to its coefficient. thus if you double a chemical equation througthout the corresponding equilibrium constant will be squared of original and if triple equilibrium constant will be cubed
if reaction is in reverse do is top and bottom in the k expression reverse and to calculate constant k
1/k
the specific heat of water
4.184 kJ/kg°C
THE NATURE OF THE EQUILIBRIUM STATE mean
Equilibrium is the state where the rate of the forward reaction is equal to the rate of the reverse reaction.At these conditions, concentrations of all reactants and products remain constant with time once equilibrium has been established at constant temperature.
SOLUBILITY AND THE COMMON ION EFFECT
Experiments show that the solubility of any salt is always less in the presence of a "common ion". Why? LeChâtelier's Principle, that's why! Be reasonable and use approximations when you can. The pH can also affect solubility. Evaluate the equation to see which species reacts with the addition of acid or base. Would magnesium hydroxide be more soluble in an acid or a base? Why? Mg(OH)2(s) = Mg2+(aq) + 2 OH−(aq) (milk of magnesia)
What is the difference between static eq
Explanation: Static Equilibrium is the equilibrium of a system at rest. Example:- A building. It is in a state of equilibrium as the forces acting on it are balanced. I'm talking about the macroscopic level; not the microscopic level of the vibrations of its solid atoms. Dynamic equilibrium is the state in which the forward and backward reactions occur at the same rate. Example:- In a closed system, the reaction between Iodine and Hydrogen in gaseous forms, to make up Hydrogen Iodide. The reactions occur at the same rate but in opposite directions.
DETERMINING Ksp FROM EXPERIMENTAL MEASUREMENTS
In practice, Ksp values are determined by careful laboratory measurements using various spectroscopic methods. Remember STOICHIOMETRY? Surely, you've made peace with the concept by now... Example: Lead(II) chloride dissolves to a slight extent in water according to the equation below. PbCl2(s) Pb+2 + 2Cl− Calculate the Ksp if the lead ion concentration has been found to be 1.62 × 10−2M. If lead's concentration is x, then chloride's concentration is 2x. So. . . . Ksp = (1.62 × 10−2)(3.24 × 10−2)2 = 1.70 × 10−5
Whether the reaction lies far to the right (favors products) or to the left (favors reactants) depends on three main factors: what are the three factor ?
Initial concentrations (more collisions--faster reaction) Relative energies of reactants and products (nature goes to minimum energy) Degree of organization of reactants and products (nature goes to maximum disorder)
K is blank and Q is blank
K-equilibrium constant Q- reaction Quotient
if K is less than one than
K>> 1 reactants are favor
equation to solve Kc
Kc=Kp(1/RT)^delta n
Kc & Kp--NOT INTERCHANGEABLE!
Kp = Kc(RT)Δn where Δn is the change in the number of moles of gas going from reactants to products: Δn = total moles gas produced − total moles gas reacting o R = universal gas law constant 0.0821 L atm/ mol K o T = temperature in Kelvin Kc = Kp if the number of moles of gaseous product = number of moles of gaseous reactant since (RT)Δn = (RT)0 = 1 Kp = Kc(RT)Δn is often referred to as the "politically correct" (pc) equation to help you remember the order of the Ks in the equation!
the relationship between Kp AND Kc is written as
Kp=Kc(0.0821)^Δn in general Kp≠Kc except in special gases where Δn = 0
EXTERNAL FACTORS AFFECTING EQUILIBRIA
Le Chatelier's Principle: If a stress is applied to a system at equilibrium, the position of the equilibrium will shift in the direction which reduces the stress Shifts occur to reestablish equilibrium positions. Think about K! Generally, products reactants Adding or removing a reagent causes the equilibrium to shift to reestablish K. As long as you milk a "mamma" cow, she keeps making more milk! Increasing pressure causes the equilibrium to shift to the side containing the fewest number of moles of gas. The converse is also true. Adding a catalyst to a reaction has causes no shift and has NO EFFECT on K. It just causes equilibrium to be established faster! Changing the temperature is a lot like adding or removing a "reactant or product". Well, as long as you think of heat energy as a "reactant" or "product".
hint for ice problems
Look for very small K values (where K < 10−5), "x" may be negligible. If "x" is large enough to impact the equilibrium values, then you must subtract it from the initial concentration. Your math will be simplified if the problem is a perfect square. If not, you must use the quadratic formula. You are allowed to use your calculator with a solver or program for solving the quadratic. If none of the initial concentrations are zero, then Q must be calculated first to determine the direction of the shift before following the above general steps.
keep in mind the equation relating to moless volume
P=(n/v)RT
USING EQUILIBRIUM CONSTANT EXPRESSIONS
Pure solids--do not appear in expression—you'll see this in Ksp problems soon! Pure liquids--do not appear in expression—H2O(l) is pure, so leave it out of the calculation Water--as a pure liquid or reactant, does not appear in the expression. (55.5 M will not change significantly) o Weak acid and weak base equations are heterogeneous [multi-states of matter; pure liquid and aqueous components] equilibria. o Solubility of salts also fits into this category. The initial solid component has a constant concentration and is therefore left out of the equilibrium expression
what can be calculated and measure any conduction not just equilibrium
Q
if Q < Ksp
Q < Ksp, the system is not at equil. (unsaturated)
(really really good ) Q tells you K tells you
Q= tells you how for a reaction is form equilibrium K= tells you where the reaction is trying to go
if top of equilibrium ratio is bigger the Q will be Q>K or Q<K
Q>K reaction will shift to left to products
What is the difference between static and dynamic equilibrium?
QUICK ANSWER In physics, equilibrium refers to the state of any object when all forces acting upon it result in zero change of motion for the object. Static equilibrium indicates that the object in question is motionless. Dynamic equilibrium indicates that the object is moving, and will continue to do so unchanged. CONTINUE READING KEEP LEARNING What does the law of inertia apply to? What is simple harmonic motion? Why does a can collapse when a vacuum pump removes air from it? FULL ANSWER Static equilibrium is generally easier for people to understand. Consider a cup on the edge of a dining room table - it is in a state of static equilibrium. The forces of gravity that would cause it to fall down are perfectly counter-balanced by the force of the table holding it up. As a result, it moves in neither direction, and will remain in this state until something changes. For example, imagine that a dog bumps the table, offsetting the balance of the cup. It topples over, rolls off the table's edge and falls to the floor. Dynamic equilibrium is a little trickier to conceptualize because examples are not as easy to imagine on earth. Imagine a jet flying through the sky when there is absolutely no air movement whatsoever (a condition highly unlikely ever to exist). In this example, the jet has four basic forces acting upon it: 1) gravity, trying to pull the jet down, 2) lift generated by the jet's wings, trying to pull it up, 3) thrust from the jet's engines, trying to propel the jet forward and 4) air resistance, trying to push the jet backwards until it stops its forward motion. As long as the jet flies perfectly level, there are no changes in the air around it, the engines produce a constant level of thrust and the force of gravity beneath it does not change, the jet will settle into a "dynamic equilibrium" where its up/down motion remains zero, and its forward motion will not change. It is moving, but the rate and direction of movement are constant.
Given that the Ksp at 298 K is 9.8 x 10-11 for the dissociation of CuCl2, set-up an equilibrium expression to solve for the molar solubility of the salt
R CuCl2 (s) ↔ Cu2+ (aq) + 2Cl- (aq) I ---- 0 0 C ---- +x +2x E---- x 2x 𝐾𝑠𝑝 = [𝐶𝑙−]2[𝐶𝑢2+] 9.8 × 10−11 = (2𝑥)2𝑥 9.8 × 10−11 = 4𝑥3 𝑥 = 2.904 × 10−4 𝑀 Here "x" represents the molar solubility of the whole salt because of the 1:1 ratio between the CuCl2 solid and the Cu2+ ion. Aka: salt particles dissolving give off a ratio of one Cu2+ ion to every one CuCl2 salt unit.
What is meant by static equilibrium?
Static equilibrium is a form of equilibrium that occurs when an object is at rest. "Static" refers to the object being motionless while "equilibrium" refers to the object either having no net forces acting upon it or having all of its net forces balanced.
What is the definition of "static equilibrium"?
Static equilibrium is a form of equilibrium that occurs when an object is at rest. "Static" refers to the object being motionless while "equilibrium" refers to the object either having no net forces acting upon it or having all of its net forces balanced.
k has no ...
UNITS
MAGNITUDE OF K--what does it mean anyway?
When greater than one, formation of products is favored. When less than one, formation of reactants is favored. Can you... 1. ...write an equilibrium constant expression? 2. ...tell how K is changed if the stoichiometric coefficients are changed on an equation? 3. ... tell how to find K for a summary equation? 4. ...tell how K depends on the way equilibrium concentrations are expressed and how to convert K in terms of Kc vs. Kp? 5. ...explain what K is telling you about a reaction?
you know the solubility rule you went over the compound that are insoluble are they really insoluble ?
You know all those solubility rules that state a substance is insoluble? They are actually a little bit soluble after all. Only the future attorneys among you read the fine print. Soluble is often defined as "greater than 3 grams dissolving in 100 mL of water". So, there is a lot of wiggle room for solubility up to 3 grams! This type of equilibria deals with that wiggle room. Apologies for "lying" to you.
