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is reversible to the neutralization. According to the structure of the molecule all

the salts can be divided into four types:

- salts of type I are formed by a strong acid and a strong base (KNO 3, BaCl 2,

etc.);

- salts of type ІІ are formed by a strong acid and a weak base (Zn (NO 3) 2,

CuSO 4, etc.);

- salts of type III are formed by a weak acid and a strong base (Na 2CO 3,

Li 2SO 3, etc.);

- salts of type IV are formed by a weak acid and a weak base ((NH 4) 2CO 3,

(CH 3COO) 2Pb, etc.).

Chemical interaction with water molecules is carried out only by ions of weak
electrolytes formed during the dissolution of the corresponding salts (supplement

D). Thus, according to the reaction mechanism the hydrolysis can be divided into
three types (salts of type I do not hydrolyze).

1 Hydrolysis of type ІІ salts

The number of hydrolysis stages is limited by the charge of a weak

electrolyte ion (cation) formed during the salt dissociation:

weak base ion
strong acid ion
2+ –
ZnCl 2 ↔ Zn + 2Cl

The first stage

ZnCl 2 + H 2O ↔ ZnOHCl + HCl,
–
+
–
–
2+
+
Zn + 2Cl + H 2O ↔ ZnOH + Cl + H + Cl ,
+
+
2+
Zn + H 2O ↔ ZnOH + H .

The second stage
ZnOHCl + H 2O ↔ Zn(OH) 2 + HCl,

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