Definitely on the Test Flashcards
le chatelier’s principle
if a reaction in equilibrium is disturbed, the reaction shifts left in order to minimize the disturbance
acid equilibrium expression
K(a) = [H3O+][A-]/[HA]
rate and temperature
higher temp. = higher rxn rate because there will be more collisions (need correct orientation)
units for rate laws (1st order)
s ^-1
spontaneity
the tendency to occur without being driven by an external force
entropy
energy and matter tend to disperse in an orderly manner
predicting change in entropy
- phase change (s - l +S; l - q +S, q - l -S)
- state of matter (solid < liquid < gas)
- atomic weight (He < Ne < Ar < Kr, Xe)
enthalpy & ∆S
if ∆H is - (exothermic) ∆S increases
if ∆H is + (endothermic) ∆S decreases
∆S equation
∆S = ∆S(final) — ∆S(inital) [J/K or J/Kmol]
direction of chemical change
entropy helps us determine the direction a rxn will proceed in (direction that increases entropy of the universe)
second law of thermodynamics
for any spontaneous process, the entropy of the universe increases (∆S > 0)
∆S and ∆H
entropy is more important than enthalpy at certain temps
equation for entropy of the universe
∆S(universe) = ∆S(system) + ∆S(surroundings)
temperature effect on ∆S
entropy depends on temperature
magnitude of ∆S(surr) is proportional to ∆H(sys)
equation for temperature effect on ∆S
∆S(surr) = -∆Hsys/T
equation for gibbs free energy
∆G(sys) = ∆H(sys) - T∆S(sys)
gibbs free energy
∆G is a value that can tell us about the spontaneity of a reaction
gibbs and spontaneity
if ∆G is + , ∆S(uni) is — (nonspontaneous)
if ∆G is - , ∆S(unis) is + (spontaneous)
STP
25° C, 1 atm, 1.0 M
∆S° equation
∆S°(rxn) = ∑n∆S(products) — ∑n∆S(reactants)
∆G° equation
∆G°(rxn) = ∑n∆G(products) — ∑n∆G(reactants)
entropy for an element
∆S° is NOT 0!
calculating ∆G at non-standard conditions
∆G = ∆G° + RTlnQ
calculating ∆G at equilibrium
∆G° = -RTlnK
∆G° = K @ equilibrium