Related Experiment Video
Updated: Apr 15, 2026
11:44
Spin Saturation Transfer Difference NMR SSTD NMR: A New Tool to Obtain Kinetic Parameters of Chemical Exchange Processes
Published on: November 12, 2016
18.8K
A Steady-State Approximation to the Two-Dimensional Master Equation for Chemical Kinetics Calculations
Thanh Lam Nguyen1, John F Stanton1
1Department of Chemistry, The University of Texas at Austin, Mail Stop A5300, Austin, Texas 78712-0165, United States.
The Journal of Physical Chemistry. A
|March 28, 2015
Summary
Solving complex chemical kinetics problems involving energy and angular momentum is simplified using a new computational approach. This method accurately predicts reaction rates and product distributions, aiding experimental analysis.
Area of Science:
- Chemical Kinetics
- Computational Chemistry
Background:
- Solving two-dimensional master equations considering both internal energy (E) and angular momentum (J) is computationally challenging.
- Accurate prediction of chemical reaction dynamics requires detailed state-resolved information.
Purpose of the Study:
- To develop and apply a simplified model for solving the two-dimensional master equation.
- To enable accurate prediction of thermal rate constants and product branching ratios.
Main Methods:
- Utilized a weak-energy/fixed-angular momentum collisional model.
- Employed the steady-state approach to solve the simplified (E,J)-grained master equation.
- Developed a predictive computational program.
Main Results:
- Obtained thermal rate constants and product branching ratios as functions of temperature and pressure.
- Demonstrated the technique's ability to yield results comparable to experimental data.
- Successfully applied the method to the reaction of singlet oxygen with methane.
Conclusions:
- The developed weak-E/fixed-J collisional model and steady-state approach provide an efficient method for solving complex chemical kinetics problems.
- The computational program facilitates the prediction and analysis of experimental chemical kinetics.
- Accurate potential energy surfaces combined with this method enable meaningful comparison with experimental results.
Related Concept Videos
01:29Reaction Mechanisms: Rate-limiting Step Approximation
79
The rate-determining step, or RDS, in a chemical reaction is the slowest step that determines the overall reaction rate. It is identified by using the observed rate law and typically involves approximation methods like the RDS approximation or the steady-state approximation.In the RDS approximation, also known as the rate-limiting-step or equilibrium approximation, the reaction mechanism consists of one or more reversible reactions near equilibrium, followed by a slower RDS, and then one or...
79
02:31Multi-Step Reactions
9.1K
Chemical reactions often occur in a stepwise fashion involving two or more distinct reactions taking place in a sequence. A balanced equation indicates the reacting species and the product species, but it reveals no details about how the reaction occurs at the molecular level. The reaction mechanism (or reaction path) provides details regarding the precise, step-by-step process by which a reaction occurs. Each of the steps in a reaction mechanism is called an elementary reaction. These...
9.1K
01:21Chemical Equilibria: Systematic Approach to Equilibrium Calculations
1.9K
Equilibrium calculations for systems involving multiple equilibria are often complex. For example, to calculate the solubility of a sparingly soluble salt in an aqueous solution in the presence of a common ion, one must consider all the equilibria in this solution. Calculations for these systems can be complicated and tedious, so a systematic approach with a series of steps is often helpful. The process is detailed below.
The first step is to identify all the chemical reactions involved, The...
The first step is to identify all the chemical reactions involved, The...
1.9K
02:20The Small x Assumption
50.8K
If a reaction has a small equilibrium constant, the equilibrium position favors the reactants. In such reactions, a negligible change in concentration may occur if the initial concentrations of reactants are high and the Kc value is small. In such circumstances, the equilibrium concentration is approximately equal to its initial concentration. This estimation can be used to simplify the equilibrium calculations by assuming that some equilibrium concentrations are equal to the initial...
50.8K
03:08Rate-Determining Steps
39.7K
Relating Reaction Mechanisms
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest step is called the rate-limiting step (or rate-determining step). A reaction cannot proceed faster than its slowest step, and hence, the rate-determining step limits the overall reaction rate.
The concept of rate-determining step can be understood from the analogy of a 4-lane freeway with a short-stretch of traffic-bottleneck caused due to...
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest step is called the rate-limiting step (or rate-determining step). A reaction cannot proceed faster than its slowest step, and hence, the rate-determining step limits the overall reaction rate.
The concept of rate-determining step can be understood from the analogy of a 4-lane freeway with a short-stretch of traffic-bottleneck caused due to...
39.7K
02:42Half-life of a Reaction
41.2K
The half-life of a reaction (t1/2) is the time required for one-half of a given amount of reactant to be consumed. In each succeeding half-life, half of the remaining concentration of the reactant is consumed. For example, during the decomposition of hydrogen peroxide, during the first half-life (from 0.00 hours to 6.00 hours), the concentration of H2O2 decreases from 1.000 M to 0.500 M. During the second half-life (from 6.00 hours to 12.00 hours), the concentration decreases from 0.500 M to...
41.2K