- Fundamental aspects
- What are c
- What is activation energy?
- Collision theory and reaction speed
- Specific rate constant of reaction (k)
- References
The collision theory exposes the principle that every chemical reaction is produced thanks to the molecules, atoms or ions of the reactants involved colliding with each other.
The clash between species will not always be the same. This will depend on the concentration and the type of reagent with which you are working.
As the concentration of reactants increases, the number of shocks increases. The opposite will happen if the concentration decreases.
This is because the higher the concentration of reactants, the greater the number of atoms and the greater the collisions with each other.
However, not all collisions are effective and therefore not all molecules that react will generate products.
If this were the case, all reactions between liquids or dissolved substances would be extremely fast, since there is greater collision between molecules in these states.
In real life, few reactions tend to form at high speeds. Many of the reactions are slow because most of the collisions produced are not effective.
Fundamental aspects
For collisions to be as effective as possible, there must be so-called effective collisions.
What are c
They are the shocks that generate products due to a reaction. These collisions are generated if two important aspects are met.
First, for the interaction to be adequate, the direction between the colliding molecules must be correct.
Second, there must be a sufficient minimum energy (activation energy) between the reacting species at the time of collision.
This energy will break the existing bonds and form new ones, since all reactions require an energy supply for the formation of products.
What is activation energy?
According to the Swedish scientist Svante Arrhenius, the activation energy is the amount of energy that exceeds the average energy level that the reactants must have, in order for the reaction to develop and the products to be achieved.
Collision theory and reaction speed
The theory of collisions is directly related to the chemical kinetics of reactions.
The reaction rate is expressed as "-r" and has to do with the speed with which any reagent is transformed per unit of time and volume.
The negative sign (-) is due to the consumption of the reagent. In other words, it is the rate at which the reactant is consumed to form the products.
For an irreversible reaction, where it is sought that all the reactant becomes a product, the reaction rate equation will be as follows: -r = k * C ^ a
In this formula "k" is the specific rate constant of the reaction and is independent. For its part, "C" is the concentration of the reagents.
The higher the concentration, the higher the collision and the higher the reaction speed.
Specific rate constant of reaction (k)
The formula for this constant is k = A * e ^ (E / R * T)
"A" is the frequency factor and has the same units as "k". "E" is the activation energy necessary for the collision to exist, "R" is the universal gas constant and "T" is the working temperature.
References
- Rate of reactions: Theory of collisions. Available at: quimicaparaingenieros.com. Retrieved December 17, 2017.
- Collision Theory.. Available at: 100ciaquimica.net. Retrieved December 17, 2017.
- Theory of collisions.. Available at: es.wikipedia.org. Retrieved December 17, 2017.
- PERRY, R. (1996) «Manual of the chemical engineer». Sixth edition. McGraw-Hill Publishing House. Mexico. Pages consulted: 4-4; 4-5.