reaction rate
- change in concentration of a reactant or product of a chemical reaction per time
rate of reaction equation
= delta (change in concentration)/ delta (time interval)
average rate of reaction
- change in reactant or product concentration over a given time interval (slope)
instantaneous rate of reaction
rate of reaction at particular time
what factors affect the rate of reactants
- chemical nature (eg. oxidization)
- concentration
- surface area
- temperature
- presences of catalyst
collision theory
theory that chemical reactions can occur only if reactants collide with proper orientation and with enough kinetic energy to break reactant bonds and form products
factors effecting collision theory
- orientation/geometry
- activation energy (minimum energy that reactant molecules must possess for a reaction to be successful
- temperature, chemical nature, SA, conc., catalyst
activated complex (part of collision theory)
an unstable arrangement of atoms containing partially formed and unformed bonds that represents the maximum potential energy point in the change- also called transition state
catalyst theory
for any reaction to occur, the kinetic energy of colliding reactant entities must be qual to or greater than the activation energy, however they do not increase the # of collisions or the kinetic energy of the between reactant entities
rate law
mathematical expression that allows calculation of reaction rate as a function of reactant concentration
rate law equation
Rate= K (A)^m (B)^n
- relationship among rate, rate constant, initial concentrations, and orders of reactions
rate constant
- k
- speed of reaction, small # is slow big # is fast
order of reaction
exponent used to describe relationship between the initial concentration and rate of reaction
total order of reaction
total sum of exponents in rate law equation ie. M +N= sum
first order reactions
^1
- same change is done to both concentration and rate ex. both are doubled
second order reactions
^2
- doubling conc. and the rate being x4
- tripling conco. and rate being x9
zero order reactions
- the rate does not change no matter what change is made to conc.
elementary step
step involving one, two, or three entity collision that cannot be explained by simpler reactions
reaction mechanism
series of elementary steps by which a chemical reaction occurs
rate determining step
step in a reaction mechanism that determines the rate of overall reaction, slowest step
reaction intermediate
an entity that is neither a recant nor a product but is formed and consumed during the reaction sequence
-present in steps but not found in final
3 kinds of elementary reactions
unimolecular- 1 reactant
bimolecular- 2
termolecular- 3 (uncommon)
the three criteria needed to satisfy an elementary mechanism
- elementary steps must add up to overall balanced equation (intermediates must cancel out)
- proposed steps must be reasonable (no termolecular)
- rate law for slow step must be the same as rate law equation for the overall reaction
