molecular weight is the weight of all the atoms in the relevant molecule.This indicator is expressed in amu(Atomic mass units).
this chemical quantities are sometimes calculated in kilograms.To this end, it is multiplied by 1.66057 * 10-27.This number is the mass of 1 amuand corresponds to 1/12 of the weight of an atom of the nuclide 12C.The most common are the relative molecular mass, which is the ratio of the weight of the molecule to the mass of one atomic unit.
It is worth noting that this figure helps characterize the mass of a molecule with all the isotopes that form the corresponding chemical compound.
The macroscopic unit amount of substance, which is called "mole" is any constant number of particles - atoms or molecules, electrons or ion pairs.This amount is 6.022 * 1023 (so-called Avogadro's number).To obtain the relative molecular weight by weight should be multiplied by the number of molecules and the result divided by the product of a constant and Avogadro one atomic mass unit.
How is the molecular weight of the substance?
The easiest way to determine this parameter is the use of a formula according to which the necessary weight of the compound divided by the amount.
If you know the chemical formula of the compound, the molecular weight can be easily determined with the help of the periodic table, because it indicates the value of each element and its serial number matches.It is enough to find the sum of the molecular weights of all components of the connection.
According to the law of Avogadro, in the same amount of gases contained the same number of molecular species.Given this pattern was derived equation Mendeleev-Clapeyron.Molecular mass of the gas can be determined by the formula.For the calculations necessary to know a lot of parameters - weight substance, the universal gas constant and temperature in degrees Kelvin, and the pressure in Pascals and the volume in m3.With this amount of data, an error in calculating the minimum, but it should be noted that equation Mendeleyev-Clapeyron valid only for gaseous substances.
molecular weight volatile compounds can be determined by mass spectrometry or gas chromatography using gas weights Martin.The average value of this index for polymeric materials with a high polymerization degree is calculated based on their rheological properties, and the properties of their solutions (e.g., viscosity, or light scattering ability).
What determines the molecular weight?
numerical value of this quantity is used to identify the various chemical compounds, but also to identify individual nucleotides in the test substance.Besides the chemical indicator is often defined in the study and synthesis of high-molecular compounds whose properties depend precisely on this parameter.
