Acids and Bases

 

(Definition-Nomenclature-Classification of Acids and Bases)

Acids:

They are the hydrogen compounds that when dissolved in water give H+ due to dissociation (Arrhenius Theory).

ACIDS - BASES - SALTS - OXIDES

Symbolism and nomenclature of inorganic acids:

Arrhenius acids have the general formula:HxA

A: it is a non-metal

Depending on the type of A, acids can be classified into two categories:

a. The non-oxygenated acids

b. Oxygenated acids

Another classification of acids:

Acids, depending on the number of H+ they yield in their aqueous solutions, are divided into monoprotic and diprotic.

Acids are also divided into strong, which we accept as completely dissociating into ions, and weak, which partially dissociate into ions. In the latter case, dimensionless molecules and ions coexist in the solution.are given below Typical examples for each case:

Strong acids: HCl, HBr, HI, HNO3

Weak acids: H2S, HCN, H3PO4

 That is, we have, HCl → H+ + Cl- (strong acid)

HCN ⇌ H+ +CN- (weak acid)

As can be understood, a solution of a strong acid e.g. of hydrochloric acid (HCl), exhibits high conductivity.

Bases:

They are the compounds that when dissolved in water give OH (

Arrhenius Theory) due to dissociation.

Symbolism and nomenclature of inorganic bases:

Arrhenius bases mostly have the general formula:M(OH)x

M: it is a metal

Note that ammonia in its aqueous solutions behaves as a base, even though it does not contain hydroxide. Hydroxide ions are formed by the reaction (ionization):

NH 3 + H 2 O ⇌ NH 4 + + OH -

Tclassification of bases:

Bases, depending on the number of OH- they yield in their aqueous solutions, are divided into monohydroxy, polyhydroxyl. Thus we have:

KOH: monoacid base

Ba(OH)2: diacid base

Acidic and Basic character:

Common properties of acids, which are due to the presence of hydrogen cations (H+) in their aqueous solutions.

These properties are:

a. Sour taste

b. They change the color of the markers

c. They react with metals (eg Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g))

d. They react with bases, thus forming a neutralization (image 1.1, 1.2).

  1.1

(Neutralization: it is the reaction of the H+ of the acid and the OH- of the base to form water.)

e. They carry the electric current and during their electrolysis, hydrogen is released at the cathode.

(Electrolysis: is the set of chemical reactions that take place during the transmission of direct current in electrolyte solutions.)

Properties of bases:

a. Soapy touch and burning taste

b. They change the color of the markers

c. neutralize acids

d. Both molten bases and their aqueous solutions conduct electricity.

Acidic solution: if the number of  H+ is greater than that of OH-

Basic solution:  if the number of  H+ is less than that of OH-

Neutral solution:  if the number of  H+ is equal to that of OH-

The pH it expresses how acidic or basic a solution is, i.e. it is a measure of its acidity.

The measurement of the pH of the solution is done with an instrument called a pH meter, which is probably the "most popular" and certainly the most necessary instrument in any chemical laboratory.