chem exam 2 Flashcards
(28 cards)
what effect reaction rates
temperature
catalysts
concentration of reactants
state/type of reactants
what is a half life
the amount of time needed to reduce a substance by 50%
how do the orders relate to half lives
0th order- half life decreases as concentration decreases
1st order- half life is constant
2nd order- hlaf life time increases as concentration decreases
what is little k
the rate law constant
what is the rate law general equation
rate law = k[a]^x[b]^y
what is collision theory
it explains why different reactions occur at different rates
what equation is used in collision theory
arrhenius - k=Ae^(-Ea/RT)
what does each letter stand for in the arrhenius equation
A- orentation
-Ea= activation energy
T- temperature
R- gas constant
what are the parts of the collision theory
-molecules must collide
- need enough energy
-orientation
how does A describe the orientation
the smaller a= the “pickier” reaction
explain molecules colliding in collision theory
if concentration increases then collisions increase then reaction increases
explain energy in collision theory
-if activation energy is higher then the rate decreases
-if temp increases the the rate increases
if a reaction is single step, how should the orders look
the orders should match the stoichiometric coefficient
what is an intermediate
a species that is produced in one step and consumed in another
- doesnt appear in overall reaction
how do you determine the higher order
by the slowest step
for an elementary step what do the reaction orders equal and proved an example
they equal the stiochiometric coefficients
ex: a->b = k[a]
ex: b+2c-> d+e = k[b][c]^2
what is physical equilibrium
forward and reverse reactions happen at the same rate but there is no chemical reaction
ex: phase changes and solubility
chemical equilibrium
forward and reverse reactions are equal and a chemical change is occuring
do equilibrium concentrations have to be the same
no
what is K
equilibrium constant
what is the general equation for K
products
_________
Reactants
how do you know if a reaction has more products or reactants
if K>1 then more products
if K<1 then more reactants
what is Kf
formation constant
what is Kd
dissociation constant
