Instruction

1

Consider, for example, reaction of sodium hydroxide with phosphoric acid. Depending on which ratio was taken as starting material, can produce different products. NaOH + H3PO4 = NaH2PO4 + H2O2NaOH + H3PO4 = Na2HPO4 + 2H2O3NaOH + H3PO4 = Na3PO4 + 3H2O

2

In the first case, for each molecule of alkali that reacts, one molecule of the acid. Therefore, the factor

**of equivalence**of sodium hydroxide equal to 1, and the factor**of equivalence of**acid and equal to 1.3

In the second case, one molecule of acid reacts with two molecules of alkali. That is, one molecule of sodium hydroxide has a 1/2 molecule of the acid. Therefore, the factor

**of equivalence**of alkali is still equal to 1, and the factor**of equivalence**of the acid is now equal to 1/2.4

Accordingly, in the third case, the factor

**of equivalence**of sodium hydroxide is 1 and the acid - 1/3, since one molecule of alkali there are three molecules of acid.5

For different classes of chemical compounds exist appropriate formula for the calculation of the factor

**of equivalence**. For example, for an item, it is calculated as: 1/V, where V – valence of the element in a particular compound. For example, the main oxide of chromium – Cr2O3. In this compound chromium has a valence equal to 3. Hence its Fe (factor**equivalence**) is equal to 1/3. But if you consider potassium bichromate (potassium dichromate) with the formula K2Cr2O7, there is the valence of chromium is 6, hence its PV will be 1/6.6

If we are talking about a simple substance, that is, such whose molecules consist of atoms of only one element, the factor

**of equivalence**calculated by the formula 1/ВхN, where the valence of the element, and N is the number of atoms in the molecule. It is easy to see that, for example, oxygen and ozone, though their composition is only one element will have a different PV. Oxygen having the formula O2 molecule, it will be equal to 1/4, and ozone with the formula O3, respectively, 1/6.