2 Chemical Kinetics Flashcards
What is chemical kinetics?
A science regarding to how a chemical reaction happens
Why is chemical kinetics important
Equilibrium does not always happen
Combustion is more often an undergoing process than an initial and final states of an equilibrium process
What is detailed chemistry?
A rigorous description of the chemical kinetics
What is reduced chemistry?
A simplified description of the chemical kinetics
What does the law of mass action state?
It states that the rate of a chemical reation is proportional to the product of the activities or concentration of the REACTANTS
When is the law of mass action applicable?
To true elementary reactions.
How do the backward and forward rate of reaction change at equilibrium?
They don’t. They’re equal
How can the progress of a backward reaction be slowed?
- endothermic
- high energy barrier
What does the SSA state?
The consumption and regeneration of intermediates occurs at equal rates such that the concentrations can be considered to remain constant.
When does the PEA apply?
To a particular reaction rath er than species
Which are the limits of SSA and PEA
They apply to vigorously burning conditions which are characterized by large temperatures and radical concentrations
Not addapted for pre-ignition and pre-extinction conditions
What’s the molecularity of a reaction?
The number of atoms or molecules that interact with each other at molecular level, leading to the completion of the reaction
What happens with higher molecularity?
The less frequnt the event
Why is a third body needed in a threebody collision?
To carry away the excess energy.
For large, complex molecules the excess energy can be absorbed by the various vibrational modes of the combined molecules and a third body may not be needed.
What does the order of reaction indicate?
The influence of the concentration of the ith reactant on the reactoin rate
How does the frequency factor A change with temperature?
It is dependent over an extanded temperature range
What does the sensitivity of a chemical reaction to temperature depend on?
To the activation energy.
The larger the (forward activation energy), the more sensitive is the reaction to temperature.
What does the activation energy present?
The minimum energy the colliding molecules must posses for the reaction to be possible.
When is the maximum reaction rate attained?
At maximum temperature
Is the backward reaction for an exothermic process slower or faster?
Slower because of the larger activation energy.
Sine the backward reaction is endothermic, the backward activation energy has to be at least as large as the heat absorbed in the reaction.
When is the backward reaction of an exothermic reaction not slow?
At high temperatures.
What does the Arrhenius number measure?
The largeness of the activation energy.
How does the reaction progress for small Ar?
The reaction rate increases progressively From T=0 to the maximum temperature
How does the reaction progress for large Ar?
The reaction rate is suppressed until T
approaches the maximum temperature ,at which t increases rapidly
The reactant is consumed rapidly within a thin layer
The reaction is confined within vers short times or within very thin space intervals
