The speed of chemical reactions is influenced by such factors as concentration of reagents, the area of their contact, temperature of a reactionary zone, existence or lack of the catalyst, etc. Speed of reactions and influence which on it is rendered by all above-mentioned factors, is studied in the special section of chemistry under the name "chemical kinetics". How it is possible to slow down reaction course?
Instruction
1. In order that chemical reaction in general became possible, it is necessary that particles of initial substances (atoms, molecules) came to contact. It is easily possible to understand that the concentration of these particles is higher (that is, the more their quantity in unit of volume), the more often there will be a contact and, respectively, reaction speed will increase. Thus, if you want to reduce this speed, you should lower concentration of reagents. For example, having increased the vessel volume where gases react, or having diluted solution where reaction proceeds.
2. There is a set of reactions which proceed with a noticeable speed only in the presence of special substances – catalysts. These substances initiate and accelerate reaction though in its process are not spent. As opposed to them, there are so-called "inhibitors" - substances which reduce speed of reaction. For example, "corrosion inhibitors" which many times over reduce the speed of oxidation of metals on air and in water are widely used.
3. Very strongly such factor as temperature influences reaction speed. For many homogeneous reactions "Vant Hoff's rule" according to which, at temperature increase by 10 degrees, the speed of reaction can increase from 2 to 4 times works so-called. Respectively, cooling of a reactionary zone will result in opposite result: reaction will slow down.
4. In laboratory practice the following method of a fast stop of reaction is widespread: place a flask or a test tube with reagents in a vessel with ice. Certainly, reactionary capacity has to be made of the refractory glass which is well maintaining sharp temperature drops.
5. In order that chemical reaction proceeded slowly, it is possible to reduce the contact area of reagents also. There is a good example: the thick log burns slowly, at first charring on a surface. If to put in a fire the thin dry branches (equal on volume to this log), they completely will burn down for much smaller time. Why so, the amount of wood is identical in both cases? And the fact is that thin branches had an area of contact with air oxygen significantly more. Respectively, and reaction of oxidation (burning) in the first case went much more slowly.