AP Chem Unit 7

26-27 Skinner GHS

open system vs closed system

open: chemicals can escape, no reversible rxns, no equilibrium. closed: opposite

at equilibrium __ are equal, NOT_

rates, concentrations

catalysts

have a neutral effect, Ae of both rxns is different and enthalpy is the same, so both benefit the same amount

increasing concentration of reactant

decreases other reactant, forward rxn favored, products increase

increasing concentration of product

increases concentration of reactants, reverse rxn favored, decreases concentration of other product

increased pressure

decreases reactants, forward rxn favored, increases products

increased temperature

increases reactants, reverse rxn favored, decreases products

law of mass action

for a reversible rxn at equilibrium + constant temp, a certain ratio of reactant:product concentrations has a constant value, k

Units for equilibrium constant

NONE!

Kc

based on concentrations, usually M at EQUILIBRIUM

what 2 things are not included in equilibrium equations

pure liquids and solids (value of 1)

Q

reaction quotient, based on mixtures not at equilibrium

large k = mostly __

products

small k= mostly

reactants

Qc < Kc

forward rxn favored

Qc = Kc

at equilibrium

Qc > Kc

rxn shifts to the reverse

reversing a rxn

reciprocal of original constant

multiplying coefficients

raise k to that power

adding reactions

multiply their Ks

K > 1

products > reactants

K < 1

reactants > products

ICE stands for

Initial, Change, Equilibrium

new equilibriums are/are not possible

are if you add a reactant

ONLY thing that can change the value of K

temperature

Le Chatelier’s principle

if an equilibrium is disturbed by changing conditions, equilibrium will shift to counteract change

when temp increases, endothermic rxns shift_

right

when temp increases, exothermic rxns shift _

left

when __ is applied, system will find a way to reduce until Kc = Qc

stress

Ksp

solubility product constant, represents max ions before precipitate appears

solubility is usually in

g/L

unsaturated

solute still dissolves

saturated

no more solute dissolves

supersaturated

becomes unstable, crystals form

increasing saturation increases _

concentration

saturated =

equilibrium

Ksp > 1 = soluble/not soluble

soluble

more soluble means __ one

closer to

common ions

formation of common solid favored

steps for common ion

1) write dissociation equation + Ksp expression

2) create an ICE table

3) plug in, assume x is small and solve

solubilities can depend on __

pH of solution

forming solvent or solute interactions is __

exothermic, ΔH < 0

breaking solute or solvent interactions is __

endothermic, ΔH > 0

ΔHsoln

enthalpy of dissolution

exothermic dissolution

ΔHsoln < 0

endothermic dissolution

ΔHsoln > 0

ΔSsoln

entropy of dissolution

gibbs free energy of dissolution

ΔG° = ΔH° - TΔS°

for a salt to dissolve, ΔG° must be

negative

going from a rigid lattice to free flowing ions __ entropy

increases