Homogeneous catalysis In some conditions, a same reaction A → B can lead to two different kinetics depending on the composition of the solution in which it is. One species C, apparently not intervening in the reaction as it is not consumed by it, increases the speed of reaction. Both reactions occur simultaneously, giving a […]
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Chapter 8: chemical kinetics – relaxation to the equilibrium
Reaction of order 1 Considering an equilibrium between two species A and B We can study the return to the equilibrium (or relaxation) after a sudden modification of the conditions such as a jump of temperature or of pressure, or the modification of an electric field. The kinetics of the relaxation towards the equilibrium adapts […]
Chapter 8: chemical kinetics – reactions in solution
The big difference between a solution and a gas is the presence of a solvent. A viscous solvent means that there are more collisions between the molecules of reactant and the molecules of solvent, slowing down the molecules. The first obligation to obtain a reaction is that the reactants have to be close to each […]
Chapter 8: chemical kinetics – kinetic theories
The following theories only apply to elementary reactions, i.e. in reactions in one step. The empirical relation of Arrhenius can be used (this relation is not limited to the elementary reactions): with kexp the kinetic constant found experimentally, Aexp the pre-exponential factor (same dimensions as kexp) and Ea the energy of activation. The goal is […]
Chapter 8: chemical kinetics – orders of reaction
Kinetics is a field of the chemistry that studies the evolution of a chemical process over time. It gives practical information on the reaction and can help to determine its mechanisms. There is already two chapters discussing the basics of kinetics (1, 2) and we will now explore a bit deeper this field of chemistry. […]
Chapter 7b : Glucose catabolism – respiratory chain
In 1935, Engelhardt analysed the rate of ATP in red blood cells (globules rouges) as a function of the rate of oxygen. The experiments showed that the ATP increases with the quantity of O2. Contrarily to the yeast, the blood cells had to be in one piece to observe the phenomenon. Even more, some enzymes […]
Chapter 4c: Solids – crystallography
A characteristic of the solids is that they have their own shape. Liquids are taking the shape of their recipient and gases take all the available space. So solids have their own shape but some are malleable, can be cut, be creased or smashed or can be very rigid. As explained at the beginning of […]
Chapter 4b: Liquids
Liquids Liquids are a condensed state: the volume of a liquid does not change by much when a pressure is applied. A liquid is a fluid: it has not its own shape and molecules can move inside it. As said previously, liquids are characterised by a short range order and a long range disorder. Properties […]
Chapter 2c: Neutralization and titration
Neutralization A neutralization reaction is the reaction occurring between an acid and a base forming a salt and water. Technically, the neutralisation is not a one step reaction in the sense that all the actions are not done simultaneously but step by step. The fist step is the dissociation of the acid and base from […]