Kinetics and Equilibrium Flashcards
kinetics
- how reactions take place and how fast they occur
reaction coordinate
- reactants
- products
- intermediates
- steps
- transition state
reaction rate
- rate law
- experimental data
- change in concentration/time
in order for a reaction to occur
- the reactants must collide
- with the proper orientation
- with a minimum energy (activation energy)
what is the middle hump in a reaction coordinate?
- intermediate
- thermodynamic quantity
- what are the two humps in a reaction coordinate?
- transition states
- kinetic quantities
catalyst
- not used up in the reaction
- regenerates itself
- does not affect intermediate
rate limiting step
- highest peak or slowest slep
reaction rate formula
rate = -1/r (Δ[R]/Δt) = +1/p (Δ[P]/Δt)
r=reactant
p=product
- rate reactants used up
- rate products formed.
rules for rate laws
- only uses reactants
- reverse reaction not considered
- no pure solids or pure liquids
- n1 +n2 + n3 = reaction order
rate constant
- proportional to the probability that a collision will result in a successful reaction
k=Ae^(-E_a/RT)
- indirectly proportional to activation energy
- directly proportional to temp and A
- NOT AFFECTED by concentration of reactants.
equilibrium
- achieved when forward rate = reverse rate
- does NOT tell us reaction rate
- reaction has not stopped
- THERMO not kinetic
equilibrium constant
- ratio of equilibrium product and reactant concentrations
Keq = [product]^P/[reactants}^R
equilibrium rules
- concentration of each species is in equilibrium
- constant ratio of products to reactants at a given temp
- no pure solids and liquids
- all capital K calculated the same way
K>1
- in equilibrium favoring products
K=1
- in equilibrium favors neither
K<1
- in equilibrium favoring reactants
reaction quotient
- Q
- concentrations when reaction is not at equilibrium
- value calculated using initial concentrations
- depends on temperature and concentration
Q>K
- NOT in equilibrium
- reaction runs in reverse
- excess of product
Q=K
- in equilibrium
Q
- NOT in equilibrium
- reaction runs forward
- excess of reactant
Free energy and reaction quotient
ΔG = ΔG^o + RTlnQ
Free energy and equilibrium constant
ΔG^o = -RT*lnKeq
LeChatelier Principle
- a system in equilibrium when stressed will shift in order to minimize that stress
add a catalyst how does the reaction change?
- it does not!
volume effects
- changing pressure stresses an equilibrium if the number of moles of gas changes in the reaction
increase pressure by decreasing volume
- shift to side with less moles of gas
decrease pressure by increasing volume
- shift to side with more moles of gas
if a reaction is endothermic
- treat heat as a reactant
if a reaction is exothermic
- treat heat as a product
respiratory equation
H2O + CO2 = H+ + CO3 2-
hyperventilating (increasing respiratory rate)
- expel a ton of CO2
- reaction runs to the left
- use up more H+
- blood becomes more alkalotic
decreasing respiratory rate
- hold onto more CO2
- reaction runs to the right
- produce more H+
- blood becomes more acidotic
formation equilibria
- equilibrium of a coordination complex is a formation constant
- reversing an equilibrium inverts the equilibrium constant
- combining multiple equilibria results in the multiplication of the equilibrium constants
solubility product
Ksp = [Sa+][Lt+]
How to predict precipitation?
Compare Qsp to K
Qsp>Ksp
- not in equilibrium
- you want to decrease the numerator so decrease the products
- therefore run reaction in reverse and solid salt will precipitate
- saturated
Qsp=Ksp
- in equilibrium
- saturated
- no more solute can dissolve
Qsp < Ksp
- not in equilibrium
- you want to increase the numerator so increase the number of products
- therefore run reaction in forward direction so more salt dissolves
- unsatured
common ion effect
- a salt’s solubility will decrease if it is added to a solution containing a common ion
- a salt’s solubility will increase if it is added to a solution containing something that removes a common ion
Dissociation constant
k2/k1=[A][B]/[AB]=Kd
Affinity constant
- the strength of binding of a molecule to ligand.
k2/k1=[A][B]/[AB]=Kaff
Relate Kaff to Kd
Kaff=1/Kd
kinetics terms
- rate
- mechanism
- catalyst
- intermediate
- transition state
- activation energy
thermodynamics terms
- stability
- equilibrium
- spontaneity
- energy
- entropy
- enthalpy
- free energy
only thing that affects both kinetics and thermodynamics
- temperature
transition states
- non isolatable species
intermediate
- generated and used it
- detectable and isolatable
raw law determined by
- rate determining step
what doesn’t affect position of the equilibrium
- solids and liquids
- inert gases
