Chemical Kinetics Flashcards
Define chemical kinetics.
The study of the time dependence of macroscopic chemical properties.
MTK, Lecture 12, Slide 12
What is the focus of Chemical Dynamics?
To interpret macroscopic properties of chemical reactions in terms of the behavior of atoms and molecules.
MTK, Lecture 12, Slide 12
True or False:
The slope of the curve of product concentration as a function of time at some time, t, is the instantaneous rate of product formation at that time.
True.
MTK, Lecture 12, Slide 13
True or False
The slope of reaction curve (concentration vs. time) approaches a horizontal line as the reaction approaches equilibrium.
True.
MTK, Lecture 12, Slide 5
True or False:
The measurement of the rate of change in the concentration of any one of the reactants or products would suffice to measure the rate of the reaction.
True
MTK, Lecture 12, Slide 13
From the definition of the “Rate Law:”
The rate law for a reaction is defined in terms of the time rate of change in the concentration of ___________________.
One of the reactants or products.
MTK, Lecture 12, Slide 14
True or False:
Generally, the rate coefficient k is not a strong function of temperature.
False.
MTK, Lecture 12, Slide 14
The order of a reaction is _______.
The sum of the exponents that describe the rate of the reaction.
MTK, Lecture 12, Slide 15
True or False:
The order of a reaction can only be determined by experiment.
True.
MTK, Lecture 12, Slide 16
True or False:
Observed rate dependence is not based solely on stoichiometry.
True.
MTK, Lecture 12, Slide 16
What are the four types of microscopic processes observed in nature?
- Zero-molecular
- Unimolecular
- Bimolecular
- Termolecular
MTK, Lecture 12, Slide 17
What are the associated molecularities of the four microscopic processes observed in nature?
- Zero-molecular –> Molecularity = 0
- Unimolecular –> Molecularity = 1
- Bimolecular –> Molecularity = 2
- Termolecular –> Molecularity = 3
MTK, Lecture 12, Slide 17
True or False:
For a zero-molecular reaction the rate is independant of the reactants or products.
True
In other words, Rate = k
MTK, Lecture 12, Slide 17
Describe a zero-molecular microscopic process.
A zero-molecular microscopic process in chemical kinetics refers to a process that involves zero reactant molecules coming together to produce a change. This may sound counterintuitive at first, as chemical reactions are generally thought to involve the interaction between reactant molecules. However, zero-molecular processes are more like spontaneous events that don’t require the collision or interaction of multiple molecules for the process to occur.
An example would be radioactive decay.
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Describe unimolecuar processes.
Unimolecular processes in chemical kinetics refer to reactions that involve the rearrangement or transformation of a single reactant molecule. These reactions are initiated by the internal energy of the molecule itself, often activated by collision with other molecules, even if those other molecules are not directly involved as reactants. Essentially, only one molecule undergoes a change to form the product(s) in a unimolecular process.
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What is the rate of a unimolecular reaction (give the equation)?
Rate = k[A]
In terms of the rate equation, unimolecular processes can often be described as first-order reactions. The rate of a first-order reaction is proportional to the concentration of the single reacting substance.
MTK, Lecture 11, Slide 17
Describe Bimolecular processes.
Bimolecular processes in chemical kinetics refer to reactions in which two reactant molecules collide and interact to form products.
Extra Notes: These kinds of reactions are often represented by second-order rate equations, although there are exceptions.
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For a bimolecular process, how is the rate equation defined?
Rate = k[A][B]
Extra Notes: Usually a second order reaction ([A]^1[B]^1 –> p = 1 + 1 = 2). There can be exceptions though.
MTK, Lecture 11, Slide 18
Describe termolecular reactions.
Termolecular processes in chemical kinetics are reactions in which three reactant molecules simultaneously collide and interact to form products.
ChatGPT.
True or False
Termolecular reactions are common.
False. These types of reactions are relatively rare compared to unimolecular and bimolecular reactions. The rarity is mainly due to the low probability of three molecules simultaneously colliding with the correct orientation and sufficient energy to trigger a reaction.
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Give the rate equation for a termolecular reaction.
Rate = k[A][B][C]
MTK, Lecture 11, Slide 18
True or False:
A fractional exponent in a rate law implies that complex mechanisms are at play.
True.
MTK, Lecture 11, Slide 19
What is the difference between a differential rate law and an integrated rate law?
A differential rate law describes the rate of a reaction.
An integrated rate law describes the time dependence of the concentration of reactants or products.
MTK, Lecture 11, Slide 20
For a zero-molecular reaction, the plots of [A] vs t is a ___________.
Linear function.
MTK, Lecture 11, slide 20
