In a school course of chemistry such term as molar concentration meets. There is it and at the textbooks in chemistry intended for students of higher education institutions. Know what is molar weight and as to calculate it, it is necessary as to the school students and students wishing to pass just successfully examination in chemistry, and that who decided to choose this science as future profession.
Instruction
1. During the experiments in analytical chemistry the sampling is very often carried out. In each of analyses, among other parameters, define amount of the taken substance. In the majority of problems of analytical chemistry it is necessary to face such concepts as mol, amount of substance, molar weight and concentration. Chemical concentration express in several ways. There are molar, mass and volume concentration. Molar concentration call the relation of amount of substance to solution volume. This concept meets it is aware of chemistry of the 10 and 11 class. It is expressed as a formula: c (X) = n(X)/V where n (X) is amount of the dissolved substance X; V-solution volume. Most often calculation of molar concentration is made concerning solutions as solutions consist of water and the dissolved substance which concentration needs to be defined. Unit of measure of molar concentration - mol/l.
2. Knowing a formula of molar concentration, it is possible to prepare solution. If molar concentration is known, then the following formula is applied to receiving solution: Cb =mb/Mb * VpPo to this formula count the mass of the substance mb, and, Vp does not change (Vp =const). Then substance of some weight is slowly mixed with water and receive solution.
3. In analytical chemistry at the solution of tasks on solutions the molar concentration and a mass fraction of substance are among themselves interconnected. The mass fraction of wb of the dissolved substance is the relation of its mass of mb to the mass of mp solution: wb =mb/mp where mp =mb+H2O (solution consists of water and the dissolved substance) Molar concentration is equal to the work of a mass fraction on solution density divided into molar weight: cb = wb Pp-pa/Mb