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aA + bB ---->cC + dDreactants are (-) and products are (+)
what does the reaction depend on
it depends on the amount of reactants that are present
method of initial rate
you measure the rate at the beginning of the reaction; after mixing the reactants, and assume that the reactant concentrations does not change enough to change the reaction rate
is the rate of a reaction changes as it poceeds it decreases. as the reactants are used up. this tells us that the rate of the reaction in general depends on the cencentration of the reactants and this gives us the rate law.
units for rate
mol/liter sec or mol/liter min
takes whatever units it must in order for the rate units to be correct, and this depends on the order of the reaction
integrated rate laws
expresses the time dependence of reactant concentrations. need reactant concentration as a function of time
first order reaction
rate = k[A]
is the amount of time it takes from the [A] = 1/2 [A]o
isomerization of cis-2-Butene
explain the series of reaction called mechanism
it must be simple. an overall reaction can be an elementary reaction, but more commonly, an overall reaction consists of series of elementary reactions that had form reactants to products. this series of reaction is called the mechanism
how do you determine validity of a mechanism
knowing the rate law
3 types of elementary reaction
unimolecular, bimolecular, trimolecular
only 1 molecule by itself react. simple, ex isomerization of cis-2-butene,and it reacts with 1st order rate laws. rate = k[A]
2 molecules (or atoms or ions) react with each other, reactions must have 2nd order rate laws. rate = k [I] [CH3Br]
3 molecules (atoms or ions) react with each other. ex have 3rd order rate law, but these are very rare (3 things collide)
is an species produced in one step of a mechanism and consumed on a later step
is a substance that increases the rate of reaction without being consumed
what is an elementary reaction
is a sone step precess whose equaation describes which nanoscale particles break apart, rearrange their positions, or collide to make a reaction occur.
the rate of the forward reaction is equal to the rate of the backward reaction
forward rate is
backward rate is
equilibrium constant and is a function of temperature only
k (c) is equal to
k (b) is < 1 then is favored to
the reactants because the products are smaller than the reactants.
k (b) is > 1 then is favored to
the products. this is a typical for reactions that go, to compleation and not equilibrium.