ap chem unit 7 equilibrium

Explain the relationship between the occurrence of a reversible chemical or physical process, and the establishment of equilibrium, to experimental observations

Q>K

favors the reverse direction, precipitate forms

Q<K

favors the forward direction, no precipitate forms

Q=K

no direction affinity, saturated, at equilibrium

exothermic reaction

negative

endothermic reaction

positive

raising the temperature of an exothermic reaction will shift the reaction in the

reverse direction

decreasing the temperature of an exothermic reaction will shift the reaction in the

forward direction

raising the temperature of an endothermic reaction will shift the reaction in the

forward direction

decreasing the temperature of an endothermic reaction will shift the reaction in the

reverse direction

reversible reactions

reactions that can take place in both directions

equilibrium

when the concentrations of the reactants and products stop changing

what is equal at equilibrium?

the rates of the forward and reverse reactions

what happens to k if you flip a reaction?

inverse. 1/k

what happens to k if you multiply a reaction by a factor?

k is multiplied by the same factor

stresses that can cause a chemical equilibrium to shift

concentration, temp, and pressure/volyme

le chatelier’s principle

when a system at equilibrium is subjected to a stress, the system will shift in the direction that tends to counteract the effect of the stress

increasing the concentration of a substance will cause the system to shift

away from the substance

decreasing the concentration of a substance will cause the system to shift

towards the substance

increasing the pressure of a system will cause the system to shift

towards fewer moles of gas

decreasing the pressure of a system will cause the system to shift

towards more moles of gas

will adding a catalyst to a system cause it to shift?

no

what does not appear in an equilibrium expression?

solids and liquids

K

deals with concentrations at equilibrium

Q

deals with initial concentrations

why are solids and liquids ignored?

their concentrations do not change significantly enough to be included

equilibrium

when forward and reverse reactions are the same, rates of reaction are equal and it may look like the reaction has stopped

parital pressure

pressure exerted by a specific gas, sum up to the total pressure

K_p = K_c(RT)^Δn

R = 0.0821 L atm/mol k

Δn = (moles of gaseous products) - (moles of gaseous reactants)

K>10

mostly products

K<0.10

mostly reactants

0.10 < K < 10

reaction moves in both directions

entropy

disorder in a system, solids more ordered than gases

gibbs free energy

determines whether or not a dissolution will be spontaneous

ΔG = ΔH - TΔS

ΔG = change in Gibbs free energy

ΔH = change in enthalpy

ΔS = change in entropy

T = temperature

If G is negative…

spontaneous, thermodynamically favorable, K>1

If G is positive…

nonspontaneous, thermodynamically unfavorable, K<1

when is an ICE table used?

when equilibrium concentrations are needed