Some chemical reactions themselves occur very difficult or did not occur.And then "rescue" come special substances - the catalysts.They allow you to "bypass the barrier" - and the reaction begins, but without them it would have either never started or would occur very slowly.Meets catalysis homogeneous and heterogeneous catalysis.What do these words mean?
name may be different depending on whether a single-phase reactants and the catalyst are.Catalyst itself is not consumed in the reaction.If you see the two-phase boundary between the substance and a catalyst, the catalysis is heterogeneous.The same can be said of the case where the state of matter and the catalyst are different.Homogenous also occurs in a homogeneous medium in a single phase.
In heterogeneous catalysis, the catalyst often - the solid, and reagents are either liquid or dissolved in a liquid, or are gases.At the same reagents are adsorbed on the active sites of the catalyst (not to be confused of adsorption and absorption. The first is a kind of "sticking" to the surface, the second-when one substance penetrates into the structure of the other).
Thus between reagent molecules and the catalyst is a chemical interaction.It may include as a chemical reaction on the surface, and weakening of the bonds in the reactant molecules.Then there is a reaction in which molecules of residual matter often hit first reactant molecules.The result of the reaction is stripped, "unstuck" from the active sites.As mentioned previously, the catalyst is not consumed in the reaction.Changing only the amount of the reactants and products.
Catalysis homogeneous and heterogeneous catalysis are widely used in industry.Here is an example of the second, as the theory we have already considered.
As is known, margarine - saturated fat.He is a solid consistency.A vegetable fat, from which it is produced mainly liquid.How to achieve hardness?With hydrogenation, ie the double bond carbon atoms are single due to the addition of hydrogen atoms.A metal acts as a catalyst of nickel in the solid state.Fats that are obtained in this reaction is called hydrogenated.Of course, like all saturated fats, they are not very useful, but to demonize them is not worth it.
Catalysis homogeneous and heterogeneous catalysis to be understood, as they help to explain not only the industry but also natural processes.For example, the destruction of the ozone layer - an example of homogeneous catalysis.
Ozone is created and destroyed again by the action of ultraviolet radiation on the molecules.However, the normal process is disrupted in the presence of molecules of chloro- and fluorocarbons, which are present in the atmosphere in the form of gases and the products of the industrial output.What happens?The molecules of chlorine and fluorine compounds of carbon are faced with the ozone molecules and take them one atom of oxygen.The compound, for example, chlorine and oxygen collides with another ozone molecule, resulting in a molecule of oxygen and regenerate the particle hlorsoedineniya which may further destroy thousands of ozone molecules.Thus there is a homogeneous catalysis.As you can see, the knowledge of this process allows us to understand that you need to be careful with the use of some deodorants and fluids for refrigerators.
However, it should be noted that the substances that provide homogeneous and heterogeneous catalysis catalysis can not only accelerate the reaction, but also to slow it.In this case they are called inhibitors.And for any catalysts, in turn, may affect certain substances: accelerators or catalyst poisons.Therefore, the process of catalysis - a multi-stage, and to understand it you need to understand the reasons for catalysis.And it is because in this process must be less than the activation energy, because the process takes a different path, than if it was in itself.
As we have seen examples of catalysis can be very different for the benefit for humans.However, in order to change the world, you need to understand it.Therefore, to study chemistry not only "vpriglyadku."