Chemical Kinetics: How fast does a reaction occur
Reading
BJU book: Ch. 14 "Chemical Kinetics"
Topics
Labs
Memo: 2020-2021 labs will include hands-on and virtual, and may vary as the Covid-19 situation changes.
Here is a list of possible labs for this lesson. I will choose from this list when we get here.
BJU book: Ch. 14 "Chemical Kinetics"
Topics
- Energy diagrams
- Rate factors
- The rate formula
Labs
Memo: 2020-2021 labs will include hands-on and virtual, and may vary as the Covid-19 situation changes.
Here is a list of possible labs for this lesson. I will choose from this list when we get here.
- The "Nitrocellulose lab" is our regular lab, but there are numerous virtual labs which cover the topics well. There are also labs you can do at home. We'll decide when we get here.
- Sodium Thiosulfate lab: This is a really good "reaction rates" lab exercise, and can be done at home. Measure the changes in reaction rate when varying temperature, and the initial concentration of reactant.
- "Reactions and Rates" PhET weblab
Below: Placing a gummy bear in potassium chlorate illustrates fast reaction kinetics. This is a fast 'oxidation' reaction... the candy provides the source of carbon, and the chlorate radical (ClO3 -) provides quick oxygen. Note: Potassium chlorate (KClO3) is a powerful oxidizer and can be dangerous. We will discuss oxidizing agents in more detail in a later session.
| 14._kinetics_class_lecture_notes__revised_2020_.docx |
Lecture outline
Thermodynamics (our previous topic) answers the question of whether a reaction will go forward or not. If the change in Gibbs Free Energy is negative, the reaction is favorable. However, we didn't discuss how FAST a reaction would occur - it might take years to go forward (the rusting of steel would be an example of a slow chemical reaction).
Kinetics (this topic) addresses the 'how fast' question. If a reaction proceeds at all, how quickly does it do so? A reaction might not have any commercial usefulness if it doesn't take place relatively quickly. Thus, the field of reaction kinetics is very important in any commercial, real-life setting.
- Reaction energy diagrams, activation energy, activation complex.
- How reaction rates are effected by concentration, temperature, surface area, and catalysts
- Reaction mechanisms, rate determining step.
- Developing the rate equation. Solving for the rate constant, 'k'.
- Reaction orders
Thermodynamics (our previous topic) answers the question of whether a reaction will go forward or not. If the change in Gibbs Free Energy is negative, the reaction is favorable. However, we didn't discuss how FAST a reaction would occur - it might take years to go forward (the rusting of steel would be an example of a slow chemical reaction).
Kinetics (this topic) addresses the 'how fast' question. If a reaction proceeds at all, how quickly does it do so? A reaction might not have any commercial usefulness if it doesn't take place relatively quickly. Thus, the field of reaction kinetics is very important in any commercial, real-life setting.
The concept of spontaneity:
- A reaction might be spontaneous, but proceed at a really slow rate. Example: rusting of iron.
- Thus, spontaneous does not necessarily mean "fast".
- On the other hand, non-spontaneous means a reaction won't go forward at all on its own. A non-spontaneous reaction needs help to get over the activation barrier. This needed "help" might be in the form of a lit match, increasing the temperature of the reactor, increasing the pressure, using a catalyst, and so on.
Nitrocellulose lab
We will make and test Nitrocellulose Guncotton.
We will make and test Nitrocellulose Guncotton.
- This is an excellent illustration of 1) a slow reaction (the nitration of cellulose), and 2) a fast reaction (the ignition of guncotton).
- Nitrocellulose was the first man-made polymer, and its history is very interesting
- We will transform cotton into a completely-new substance which looks like cotton, but has different texture and properties!
- This is done by attaching nitrate (NO3) radicals to the cotton! This gives it some *interesting* new properties.
"Reactions and Rates" PhET WebLab
The answer key is provided for guidance. You still need to do your own work!
https://phet.colorado.edu/en/simulation/reactions-and-rates
The answer key is provided for guidance. You still need to do your own work!
https://phet.colorado.edu/en/simulation/reactions-and-rates
| 14._reactions_and_rates_phet_weblab.docx |
| 14._reactions_and_rates_phet_weblab__answer_key_.docx |
NASCAR Chemistry Problem
| 14._nascar_chemistry_problem__revised_.docx |
| 14._the_chemistry_of_nascar.pdf |
Kinetics Homework
| 14._kinetics_homework_problems.docx |
| 14._kinetics_homework_webinar_notes.docx |
The Coca-Cola research assignment (below) will require Internet research. Use search terms such as "digestion of sucrose", "digestion of carbohydrates", "metabolism of sucrose", etc. Also read the "Chemistry of Digestion" paper, below.
| 14._coca_cola_research_assignment.docx |
| chemistry_of_digestion_-_american_chemical_society.docx |