AP Chemistry: Equilibrium

chemical equilibrium (dynamic equilibrium)

chemical equilibrium (dynamic equilibrium)

two exactly opposite reactions are occuring simultaneously with the same rates of reaction

equilibrium constant (Kc, Kp)

the reaction quotient at equilibrium

reactant quotient (Q)

fraction relating the products ad reactants

at equilibrium are the concentrations of the chemical species equal

not necessiraly, they are constant

what states of matter are not included in an equilibrium equation

liquids and solids

if the K value is large

there are more products than reactants; reaction lies to the right

if the K value is small

there are more products than reactants; reaction lies to the left

Le Châtelier’s principle

if a chemical system at equilibrium is stressed, it will reestablish equilibrium by shifting the reactions involved

what are examples of stressors on equilibrium

changes in concentration, pressure, and temperature

are changes in pressure significant in all equilibrium reactions

no, only if gases are involved

if the volume a container decreases, how will the equilibrium system shift?

to the side with less moles of gas

if the volume a container increases, how will the equilibrium system shift?

to the side with more moles of gas

what factor changes the value of the equilibrium constant

temperature

heterogeneous equilibria

equilibria that involve more than one phase

homogeneous equilibria

• systems in the gas phase, where all reactants and products are gases

what shift occurs when Q=K

no shift

what shift occurs when Q>K

shift right to left

what shift occurs when Q<K

shift left to righ

saturated solutions are at

equilibrium

shift right meaning

there are not enough products, so the system will shift to consume reactants and produce more products

shift left meaning

there are not enough reactants, so the system will shift to consume products and produce more reactants

what type of solution is at equilibrium

a saturated solution

if K >1, what side of the reaction is favored

products (forward reaction) is favored

if K is very large, describe the reaction

reaction goes essentially to completion

if K <1, what side of the reaction is favored

reactants (reverse reaction) are favored at equilibrium

if K is very small, describe the reaction

reaction barely proceeds at all

relate the K of the reverse reaction to that of the forward reaction

it is the reciprocal

when the equation of reaction is multipled by n, what happens to K

K is put to the nth power

when elementary steps are added together, the K of the overall reaction is

the product of the K’s of the elementary steps

if the pressure is increased, how will the equilibrium system shift?

to the side with less gas moles

if the pressure is decreased, how will the equilibrium system shift?

to the side with more gas moles

if an inert gas is added, how will the equilibrium system shift?

no effect

if heat is added to an endothermic reaction, how does K change?

K increases (K>1)

if heat is added to an endothermic reaction, how does the equilibrium system shift?

to the right (forward direction)

if heat is added to an exothermic reaction, how does K change?

K decreases (K<1)

if heat is added to an exothermic reaction, how does the equilibrium system shift?

shift to the left (reverse direction)

when concentration changed, the system will always shift away from

the added component

diluting always shifts towards which type of species

aqueous species

concentrating always shifts towards which type of species

less aqueous species

if the amount of a liquid or solid is changed in a system, how does the system react?

no change

how does adding a catalyst affect the equilibrium system?

no change

Ksp

solubility product constant

how does having more anions and cations affect the Ksp value?

the Ksp value is increased

solubility (s)

concentration of solid that dissolves

how does solubility affect the value of the equilbrium constant?

it has no effect, the attainment of equilibrium can be affected however

the Ksp of two salts can only be compared with

salts that fall into the same number of ions

a bigger Ksp value means

more soluble

when tow salts have a different number of ions, how can their solubilities be compared

by solving for solubility

what happens when Q is greater than the Ksp

precipitation

when happens when Q is less than the Ksp

no precipitate

common-ion effect

when a solid is dissolved in a solution with either the cation or anion already present, less solid will dissolve

how does the common-ion effect affect the Ksp?

no change

how does increasing pH affect the solubility of a salt?

decreases the solubility

how does decreasing pH affect the solubility of a salt?

increases the solubility

adding a substance that is not in the equilibrium equaiton increases the change of

a reaction with the substance