AP Chem Unit 7: equilibrium

equilibrium expression

products in numerator, reactants in denominator

K_eq>1

numerator in equilibrium expression is greater (products), products are favored. this means more products than reactants present

products are favored at equilibrium

K_eq<1

denominator in equilibrium expression is greater (reactants), reactants are favored. this means more reactants than products present

reactants are favored at equilibrium

K_eq will only change with

(K_eq is always at equilibrium) temperature bc this changes the energy of the system

K_c

constant for molar concentrations

K_p

constant for partial pressures

K_sp

solubility product, which has no denominator because reactants are solids

K_a

acid dissociation constant for weak acids

K_b

base dissociation constant for weak bases

K_w

describes ionization of water (1 × 10^-14)

rules to manipulate K_eq

1. if you reverse rxn, take reciprocal of its equilibrium constant to get new constant

2. if you multiply a reaction by a coefficient, raise equilibrium constant to the power of that coefficient to get the new one. ex: multiply by 2, raise K_eq²

3. if you add two rxns together, multiply their equilibrium constants to get the new one

Q will change with…

(anytime in reaction, Q is rxn quotient) changes with concentration, pressure, and temp

Q>K_eq

excess of products. rxn has to go in reverse (left normally) to go back to equilibrium

Q<K_eq

excess of reactants. rxn has to proceed foward (right normally) to reach equilibrium

add reactant

system right

remove reactant

system left

add product

system left

remove product

system right

if substance is added, system shifts…

to the other side of where substance is added

if volume goes down…

pressure goes up, system favors side with fewer mols of gas

if volume goes up

pressure goes down, systen favors side with more mols of gas

if a nonreacting gas is added…

total pressure remains the same, the partial pressures decrease

if there are different numbers of aqueous species on either side of the reaction, dilution will cause a shift to the side with…

more aqueous species

changing temp of system changes

the energy of the system

K_eq decreases at

a higher temp

K_eq increases with a

lower temp

K_sp is a

measure of the extent of a salt’s dissociation in solution

molar solubility

amount of solute that can dissolve to make one liter of a saturated solution

molar solubility of most salts increases with

rising temperatures. bc higher temp has more energy available to force water molecules apart to make room for solute ions

when two salt solutions that share a common ion are mixed…

the salt with the lower value for K_sp will precipitate first