Regarding the hydrolysis of certain salts
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I have a question regarding chemical theory: for certain salts such as NaCl, they do not undergo hydrolysis in water, but they dissolve in it. Is there a difference between these two phenomena? Don’t all salts dissolve in water? Isn’t the hydrolysis of salts different from their dissolution? If anyone knows, please let me know. Thank you
The dissolution of salt and its hydrolysis are two different processes. Dissolution refers to the process in which salts disperse into ions in water; for example, when table salt NaCl dissolves in water, it forms Na+ and Cl- ions. Hydrolysis, on the other hand, is a chemical reaction in which the ions of salts dissolved in water react with water molecules to form new substances. Not all salts undergo hydrolysis. For example, table salt NaCl does not hydrolyze in water; it only dissolves without forming any new substances. Some salts, such as sodium carbonate Na2CO3, undergo hydrolysis in water to produce carbonic acid and sodium hydroxide. In short, dissolution is a physical process, while hydrolysis is a chemical reaction. .
The hydrolysis of salts in water is related to their solubility, but it mainly depends on the properties of the ions that make up the salt. For example, in salts formed from strong bases and weak acids, it is the anion that undergoes hydrolysis; the weaker the acidity of the weak acid, the greater the degree of hydrolysis. Acetic acid is more acidic than carbonic acid, so sodium carbonate hydrolyzes more easily than sodium acetate. In salts formed from strong acids and weak bases, it is the cation that undergoes hydrolysis; the weaker the basicity of the cation, the greater the degree of hydrolysis.
Are the solubilities of salts of strong acids and strong bases very low?
Dissolution and hydrolysis are two distinct chemical processes (the dissolution of some substances is a physical process). In the process of dissolution, the solvent merely serves to disperse the molecules or ions of the solute within it; sometimes, energy changes also occur as a result. However, in hydrolysis, the solvent—water—is involved in all or part of the chemical changes of the solute, and a new substance is formed; this new substance is the hydrolysis product. Regarding salts, hydrolyzable salts need to meet the conditions necessary for hydrolysis; these include the chemical composition of the salt itself, as well as the presence of conditions that allow the formation of hydrolysis products. Dissolution certainly takes place in a solvent, but hydrolysis does not necessarily occur entirely in liquid water; it can also take place in a humid environment.