Chapter 12 Flashcards
Chemical kinematics
The study of the speed that reactants are converted to products in a chemical reaction.
Factors that have a role in the speed of a reaction and its effectiveness
state of matter, particle size, temperature, concentration, presence of catalyst
Spontaneity is not related to?
speed
Spontaneity
a measurement of possibility that the reaction will happen at the current conditions
What is maintained when a reactant is converted into a product in a chemical reaction?
stoichiometry ratio
Reaction rate is based on?
a change in concentration over time
Rate always _______ with time
decreases
Why do expressions involving reactants have negative values?
because rate always decreases with time
Calculated rates will always have?
positive values
Rates do not have to be?
constant
Rates follow an?
pattern or predictable pathway
The reverse reaction affects?
the rate of change in concentrations
If we take the reverse reaction into consideration, the overall change in concentration depends on?
the difference in the rates of the forward and reverse reaction
What is the issue when looking at reverse reactions?
where to study the reactions when looking to calculate a rate law
To avoid confusion, we study the rate of a reaction under what kind of conditions?
where the reverse reaction is negligible
The rate law depends on?
REACTANTS ONLY
Rates will be ______ rates.
instantaneous
instantaneous rates will be measured at a time where?
the reverse reaction has not contributed to the overall rate
In the rate equation, O order means?
there is a catalyst
The rate equation is _____ dependent.
reactant
In the rate equation, the order of the reactant is determined how?
experimentally via data and calculations
In the rate equation, k is?
the proportionality constant or rate constant.
In the rate equation, n is?
the order of the reactant
In the rate equation, the integer value can be?
0 or even a fraction.
What are the types of rate laws?
differential and integrated
differential rate law is also called?
rate law
differential rate law involves only?
reactant concentrations
integrated rate law involves only?
time and entire reaction
differential rate law
expresses how the rate of a reaction is dependent on the concentration of the elements or compounds in the experiment.
integrated rate law
expresses how the concentration of a species in a reaction changes with time.
species
reactant or product
choice of rate law type depends on?
what data is easiest to collect.
the value of n also tells us?
what power to raise the law to
3 options of integrated rate law?
0, 1, 2
reaction mechanism
series of steps a reaction takes
2 key components of a reaction mechanism
must use a balanced equation and mechanisms have to match the rate law
intermediates
elements or compounds formed and consumed during a reaction that do not make it in the final equation.
When looking at rate orders you should not pay attention to?
stoichiometry ratio
elementary steps
unfinished reaction mechanism
molecularity
the number of species that must collide to produce the reaction indicated by that step
unimolecular step
a reaction involving 1 molecule
bimolecular step
a reaction involving the collisions of two species
termolecular step
a reaction involving the collisions of three species
Which is the most important step?
rate determining step
Rate determining step
slowest step in the process and all reactions must get past this step before they can produce products
the rate determining step determines
the rate for the reaction
collision model
molecules must collide in order to react, they must collide with sufficient energy and proper orientation
In the collision model, if the proper conditions are not met the molecules will?
attempt to react again until they get things right
activation energy
the energy required to convert atoms or molecules to the activated complex
activated complex
transition state
the activation energy is the minimum energy required for?
an effective collision
The activation energy value is influenced by factors such as
temperature, catalysts, and pressure
catalysts
substances that speed up a reaction without being consumed or changed themselves
Catalysts are mostly?
metals
catalysts can also?
lower activation energy and keep rate constant
heterogeneous catalysis
scenario where the catalyst is in a different phase than the reacting substances
heterogeneous catalysis are usually?
gaseous reactants on a solid surface
uses of a heterogeneous catalysis
-conversion of alkenes to alkanes
-conversion of CO and NO in auto exhaust to CO₂ and N₂
-process is referred to as adsorption
homogeneous catalysis
reactants and catalysts are in the same phase
example of homogeneous catalysts
decomposition of Ozone by CFC’s
