Unit 7: Equilibrium

(7.1) Introduction to Equilibrium (7.2) Direction of Reversible Reactions (7.3) Reaction Quotient and Equilibrium Constant (7.4) Calculating the Equilibrium Constant (7.5) Magnitude of the Equilibrium Constant (7.6) Properties of the Equilibrium Constant (7.7) Calculating Equilibrium Concentrations (7.8) Representations of Equilibrium (7.9) Introduction to Le Châtelier’s Principle (7.10) Reaction Quotient and Le Châtelier’s Principle (7.11) Introduction to Solubility Equilibria (7.12) Common-Ion Effect

what type of reaction can reach equilibrium?

reversable

equilibrium

specific scenario where the rate of the forward and reverse reaction are equal

in what kind of system can equilibrium occur?

closed system—no outside interactions can interfere with reaction

concentrations of species at equilibrium

remain constant

do [reactants] = [products] at equilibrium

not necessarily, but their respective concentrations should be constant

rates of reactions at equilibrium

rate of forward = rate of reverse, and the rate is non-zero

factors that affect vapor pressure

temperature and IMFs

if [products] > [reactants] at equilibrium,

forward reaction favored

if [products] < [reactants] at equilibrium

reverse reaction favored

if [products] = [reactants]

neither forward/reverse reaction favored

increasing temp favors which reaction

endothermic reaction

decreasing temp favors which reaction

exothermic reaction

increasing volume favors which reaction

the side with more moles of gas (want to increase pressure)

decreasing volume favors which reaction

the side with less moles of gas (want to decrease pressure)

equilibrium constant

denoted K_eq, [products]/[reactants] at equilibrium

reaction quotient

denoted Q, [products]/[reactants] at anytime

which states are included in K or Q

aqueous and gas

K_c =

\frac{\left\lbrack C\right\rbrack^{c}\left\lbrack D\right\rbrack^{d}}{\left\lbrack A\right\rbrack^{a}\left\lbrack B\right\rbrack^{b}}

K_p =

\frac{\left(P_{C}\right)^{c}\left(P_{D}\right)^{d}}{\left(P_{A)}\right)^{a}\left(P_{B}\right)^{b}}

if K > 1

products favored, forward reaction favored

if K < 1

reactants favored, reverse reaction favored

if K = 1

neither products nor reactants favored

if Q < K

forward reaction favored

if Q > K

reverse reaction favored

if Q = K

reaction at equilibrium

if given only the inital amounts of reactants, assume

initial amount of product is 0

K_eq of reverse reaction

1/K_eq

K_eq to double coefficients of reaction

(K_eq)²

K_eq of an overall reaction with multiple steps

multiply individual K_eqs

how to read equilibrium graph (concentration or pressure vs. time)

equilibrium reached when lines plateau

what happens to an equilibrium graph when a stress is applied

line jumps up/down then levels out

le chatlier’s principle

when a stress if applied on a reaction at equilibrium, the reaction will shift to accomodate the stress

catalyst effect on equilibrium

no change

what factor changes K

temperature only

what factor changes Q

any stress

solubility equilibria

equilibrium for a solid that dissolves into an aqueous solution

solubility product constant

denoted K_sp, equilibrium constant for dissolution of a solid

closer K_sp is to 1 means

that solid is more soluble

if Q < K_sp

solution is unsaturated, no precipitate

if Q ≥ K_sp

solution is saturated, precipitate forms

molar solubility

denoted s or x, molarity of solute in saturated solution

solubility

grams of solute in 1L of saturated solution

unsaturated solution

less than the max amount of solute dissolved

saturated solution

max amount of solute dissolved, the addition of more solute will settle at the bottom

effect of temperature on the max amount of solute able to be dissolved

raising the temp raises the max amount

at equilibrium of the dissolution of solid,

rate of dissolution = rate of crystallization; [aqueous ions] remains constant

common ion effect

when salt with a shared ion added to a solution, the solubility of the original salt decreases