The molecular mass of any substance is meant as the total atomic mass of all chemical elements which are a part of this substance. To calculate the molecular mass of substance, special efforts will not be required.
It is required to you
- Mendeleyev's table.
Instruction
1. As it was told in definition, molecular weight is the sum of all atomic masses of substance. To learn atomic masses of various chemical elements, it will be required to look at the periodic table of chemical elements of Mendeleyev.
2. Now it will be required to throw a stare on any of elements in this table. Under the name of any of the elements specified in the table there is a numerical value. It also is the atomic mass of this element.
3. Now it is worth sorting several examples of calculation of molecular weight, proceeding from the fact that atomic masses are known now. For example, it is possible to count the molecular mass of such substance as water (H2O). The molecule of water contains one atom of oxygen (O) and two atoms of hydrogen (H). Then, having found atomic masses of hydrogen and oxygen according to Mendeleyev's table, it is possible to begin to consider also molecular weight: 2*1.0008 (hydrogen molecules two) + 15.999 = 18.0006 and. e. m (atomic units of mass).
4. One more example. Usual table salt (NaCl) will be the following substance which molecular mass can be counted let. Apparently from a molecular formula, the molecule of table salt contains one atom of Na sodium and one atom of Cl chlorine. In that case, its molecular weight is considered so: 22.99 + 35.453 = 58.443 and. e. m.