you need
• - Calculator;
• - periodic table
Guide
1
To be able to find an equivalent of a substance, you should use the formula: 1 / z (a substance), where 1 / z - factor equivalence(fe), that is a number that indicates how much of the particulate matter equivalent equivalent.This value is always less than or equal to one.Simply put, the equivalence factor - it is a factor that is written directly to the formula in finding the equivalent substance.For example, you need to find the equivalent of phosphoric acid in its interaction with sodium hydroxide.Write down the reaction equation: 2NaOH + H3PO4 = Na2HPO4 + 2H2OOtsyuda seen that sodium atoms are replaced by only two hydrogen atoms, that is, a dibasic acid (involved in t
he reaction 2 H + ion).Thus, by definition, will be equivalent to a conventional phosphoric acid H3PO4 ½ particle.
2
Note that the equivalent of one and the same substance varies depending on the type of reaction in which a substance enters.Furthermore, equivalent elements depends on the type of compound, which is included.Take the same materials as in the previous case, but the reaction may go differently: 3NaOH + H3PO4 = Na 3PO4 + 3H2O.Zdes fe (H3PO4) = 1/3, fe (NaOH) = 1.Consequently, the equivalent of phosphoric acid - H3PO4 particle 1/3, and is equal to one equivalent of alkali.
3
order to successfully find the equivalents of different substances you need to remember the formula for finding fe depending on the type of chemical compound.So much for the simple elements, fe = 1 / valence of the element.Example: fe (H2SO4) = 1/6, and the equivalent sulfur H2SO4 equals 6. For salts - fe = 1 / n (meth.) - B (meth.) = 1 / n (kp) - B (kp), where n (meth.) - the number of metal atoms, B (meth.) - valency of the metal, n (CO) - the number of acid residues, B (KO.) - valency acid residue and T.d.
4
difficult to find the equivalent of the substance in the reactions of the redox type, since the calculation you lead in the number of electrons that are involved in the reduction or oxidation.Given the task to find the equivalent of manganese hydroxide in the reaction: 2Mn (OH) 2 + 12NaOH + 5Cl2 = 2NaMnO4 + 10NaCl + 8H2OIz equation that gives 5 manganese electrons changes from Mn +2 in Mn +7.Hence, the equivalence factor Mn (OH) 2 - 1/5, and the equivalent of hydroxide is 5.