chapter 12: Chemical Equilibrium Flashcards
what is a reversible reaction
reaction that can proceed in both the forward and reverse direction
what happens as the forward reactions slows
the reverse reaction accelerates and they reach the same rate
what is a dynamic /chemical equilibrium
rates of the forward and reverse reaction are equal
in chemical equilibrium are the concentrations equaling each other
No, but they remain constant
what is the law of mass action
rates of the forward and reverse rxns are equal but not the concentrations
who discovered the law of mass action
cato guldberg and peter waage
what letter represents the constant
K
what will affect K
temperature
what is the Kc constant expression
[Products] / [reactants]
if the temperature is constant then what happens to Kc
Kc is constant
what happens when an equilibrium constant expression is written backward
then you need to find the inverse of the o.g reaction
when manipulating K reactions do you multiply or add the ks together
multiply them
what do you do when a balanced chem is multiplied by a factor
the equilibrium constant is raised by that factor
what is the concentration of gas in a mixture proportional to
the partial pressure
what is the constant expressions of Kp
(partial pressure products) / ( partial pressure of the reactants)
what can we use to find the pressure in an equation
p=nRT/v
what is the number for r
r = 0.08206
what is the equation for Kp and Kc
Kp = (RT) ^(change in moles)
how do you find the change in moles
( moles of gas product)- (moles of gas reactant)
when does Kp = Kc
when the change of moles is 0 ( same # of moles of gas appear on both sides of the balanced chem equation)
what is a homogenous equilibria
substances all in the same phase
what is a heterogenous equlibria
involves substances that are in different states
what states are not involved in an equilibrium reaction
solids and liquids
3 reasons its good to know the equilibrium constant
a. ) whether the concentrations represent an equilibrium condition
b. ) the tendency of the reaction to occur
b. ) the equilibrium position that will be achieved
what is K constant not related to
the time required to reach the equilibrium
what does time depend on
the reaction rate, due to the size of the activation energy
if K is greater than 1 what does that mean
the reaction is product favored bc there is a greater concentration of products than reactants
if K «_space;1, what does that mean
the reaction is reactant favored, the concentration of reactants is greater than the
what can help us predict the direction of the reaction
Qc
what will the system do if one of the reactants or products is 0
it will shift to produce the missing component
how can Qc be found
substitute the initial reactant and product concentrations or partial pressures into an equilibrium-constant expression
what does it mean if q =k
reaction is at equilibrium, there is not shift
what does it mean if q is less than K
reaction will shift to the products
what does it mean if q>k
reaction will shift to the reactants
what do we use when calculaing Kc when one equilibrium concentration is known
an ICE table
what are the steps for calculating an ICE table
- ) write down all known initial and equilibrium concentrations
- ) calculate the change
- ) use the coefficients of the reaction to calculate C for the remaining
- ) calculate E
steps for calculating eq. conc. from the initial concentrations
- ) treat the change in the concentration as X
- ) use the coefficients from the balanced equation for the coefficient of X
- ) X is positive for for products and X is negative for reactants
- use the quadratic formula to solve
if Kc is small, how does that affect the large initial concentrations of the reaction
the reactant concentration will not change significantly
how to check the validity of the approximation
approximate / initial conc. x 100 = <5%
who discovered Le Chatelier’s principle
Henri-louis le chatelier, the french chemist
what is Le Chatlier’s principle
- ) system starts at equilib.
- ) a change in the system cab be made by concentration, volume, pressure, temp, catalyst
- ) system responds by shifting to the right (prod) or left(react) to restore equlibrium
what does le Chatlier say about adding a substance even at equilibrium
add a substance, the reaction will shift to re-establish equilibrium by consuming part of the added substance
ex: adding reactant = decrase the amounts of other reactant = shift towards the product
why does adding a reactant increase the rate of the forward reaction
bc when you add more reactant then Qc is getting smaller than K so then we shift to the products
what happens when you remove a substance from the reaction
move in the direction that forms more of that substance
ex: removing a reactant will shift to replace it and it will increase the reactants
- decreases the rate of the reaction
where is hemoglobin found
protein that is found in red blood cells that reacts with O2
what is the purpose of hemoglobin
enhances the amount of O2 that can be carried through the bloodstream
what happens when a system’s volume decreases
pressure increases, system will shift towards the fewer moles of gas
what happens when a systems volume increases
pressure goes down, shift toward more moles of gas
what effect does pressure and volume have on equlibrium
they have no effect bc changing the size of the container has no effect
what is boyle’s law
decreasing the containter volume = increasing the total pressure
what is dalton’s law of partial pressures
total pressures increase = partial pressures of all gases increase
decreasing the container volume does what
- increase concentration of all gases
- same # of moles but different number of liters = different molarity
what does adding a gas reactant do
increase the partial pressure bc equil. will shift to the right
what will an inert/ unreactive gas do to the equilibrium
no effect
what happens in an endothermic reaction
- heat is absorbed
- heat is used to convert reactants into products
- heat is a reactant
what does an endothermic reaction do to K
increasing the temp causes the equi. to shift to the right (products) so K increases
what happens in an exothermic reaction
- heat is released
- heat is treated as a product
what happens to K in an exothermic reaction
equi. shifts to the left(reactants) b bc K decreases
what happens to the equilibrium from heat being added
shift away from the added heat
does a catalyst affec the position of equilibrium
no
endothermic; increase temp
shift right, k increases
endothermic; decrease temp
shift left, k decreases
exothermic; increase temp
left, k decreases
exothermic; decrease temp
right, k increases
more moles of gas on right; increase volume
shift to the right, no effect on K
more moles of gas o right; decrease volume
shift to the left
more moles of gas on the left; increase volume
shift left
more moles of gas on the left; decrease volume
shift right
