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Kinetics
kinetics is the study of the factors that affect the speed of a reaction and the mechanism by which a reaction proceeds
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4 factors that influence the speed of a reaction:
- nature of the reactants (physical states (s,l,g) surface area)
- temperature,
- catalysts,
- concentration
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what do catalysts do
speeds up the reaction by lowering the activation energy
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There are three types of reaction rates
1) Average Rate: 2) Instantaneous Rate: 3) Initial Reaction Rate:
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2) Instantaneous Rate:
Provides the rate of a reaction at a given moment.
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3) Initial Reaction Rate: .
Is the instantaneous reaction rate at the moment the reaction starts
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Instantaneous Rate - Determined from the
slope of a tangent to the concentration vs time curve at a specified time.
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Rates of reactions depend on
concentration of reactants
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The more starting material you have, the------------ a reaction will proceed.
faster
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Second order – rate quadruples when ---------- concentration (exponential)
- doubling
- M/s = k (M)2 k = M-1s-1
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Zero order = relationship to concentration?
- independent of concentration
- Rate = k[A] M/s = k (M) k = M/s units
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Most reactions do not contain
only one reactant
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Reaction (Rate) Constant -
A proportionality constant relating the concentrations to the reaction rate.
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If x,y, and z are added together, what does that equal
the total
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Half-Life, t1/2 -
time required for the concentration or amount of a sample to decrease by 50%. One-half of the sample reacts each half-life.
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The minimum amount of energy required to reach the transition state is referred to as the
Energy of Activation.
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Upon collision, a chemical reaction occurs as reactants pass through ------------in which bonds are being broken and new bonds are being formed.
a transition state
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The rate of a chemical reaction is dependent upon ------------
its energy of activation.
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Those reactions that have a high energy of activation tend to proceed -----------
slowly
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Reactions that have a small energy of activation tend to proceed ------
rapidly
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A catalyst is a substance that
speeds up a reaction but is not consumed in the process. (lowers activation energy required)
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elementary steps, meaning that they cannot ------and that the molecules actually------------
- 1be broken down into simpler steps
- 2interact directly in this manner without any other steps
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molecularity
the number of reactant particles in an elementary step
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a unimolecular step involves -------------
a bimolecular step involves-------------
- 1 reactant particle
- 2 reactant particlesthough they may be the same kind of particle
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rate determining step
- the slowest step has the largest activation energy
- product production cannot occur any faster than the slowest step – the step determines the rate of the overall reaction
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