The equivalent of substance is a conditional or real particle which can release, attach or any other way to be equivalent to the hydrogen cation participating in ion-exchange reactions or an electron in oxidation-reduction reactions. At the solution of tasks mean the equivalent molar mass of substance by an equivalent of substance.
It is required to you
- - molar weight;
- - valency;
- - acidity;
- - basicity.
Instruction
1. Equivalent weight is one of the most important characteristics of substances. At the solution of tasks it is designated as M ekv. The molar mass of an equivalent of any connection, proceeding from a chemical formula of the studied substance and its belonging to a certain class of chemical compounds is defined.
2. Successfully to find the molar mass of equivalents, you will need to know such indicators as molar weight – weight of one mole of a substance. Basicity of acid – amount of atoms of hydrogen which acid can attach. The acidity of the basis is defined by quantity of ions of OH-. Valency – quantity of chemical bonds which forms atom with other elements in connection.
3. The formula of finding of equivalent mass of substance depends on to what class the studied connection belongs. For example, for finding of an equivalent of substance at oxides, you will need to divide a molar lot of connection into the number of atoms of oxygen which is previously increased by two. For example, for Fe2O3 iron oxide equivalent weight will equal 56*2 + 16*3/3*2 = 26.7 g/mol.
4. For finding of molar mass of an equivalent of substance at the basis, divide the molar mass of the basis into its acidity. So, for the basis of Ca (OH) 2 the equivalent will equal 40 + (16+2)*2/2 = 37 g/mol.
5. To find a substance equivalent for acid, you will need to make the following action: divide the molar mass of acid into its basicity. For finding of molar mass of an equivalent of substance of sulfuric H2SO4 acid divide 1*2 + 32 + 16*4/2 = 49 g/mol.
6. At last, for finding of an equivalent of substance of salt divide the molar mass of substance into the number of atoms of metal multiplied by its valency. For example, molar mass of an equivalent of substance of Al2(SO4) 3 salt = 27*2 + (32 + 16*4)*3/1*2 = 171 g/mol.