Properties of Acid and Base in Chemistry
Properties of acids and bases are opposite in nature to each other in the chemical reaction of acid base solution. According to Arrhenius’s acid base definition in inorganic chemistry, acids dissociate hydrogen ion whereas bases hydroxyl ion in water solution. But due to limitations, we can not explain acidic and basic properties or the nature of acids and bases neutralization reaction by only one theory. For example, sulfuric acid, nitric acid, and hydrogen chloride show acidic properties only when it dissolved in water solution but if we use organic solution or gases, it does not consider as an acid according to Arrhenius. But acids and bases are the following common properties for the general study of chemistry.
- Acids are the chemical elements or substances whose aqueous solution is sour in nature and turns blue litmus to red.
- Bases are the elements or substances whose aqueous solution is slippery nature, bitter teste, changed the color of the litmus to blue, and reacts with acids to form salts.
To better describe all the properties, definitions, redox reactions and chemical bonding on orbital of acids and bases, we need to know about five theory like Arrhenius definition in the solution, Protonic definition, Lewis definition, and hard soft acid base theory
Properties of Arrhenius Acid and Base
Arrhenius defines acid base properties in water solution only. According to his definitions, an acid when dissolved in water, dissociate hydrogen ions and anions but a base when dissolved in water dissociate into hydroxyl ions and cations. Therefore, NaOH neutralizes hydrogen chloride, but this acid base neutralization reaction involving the combination of hydrogen and hydroxyl ions to form water.
HCl → H+ + Cl–
NaOH → Na+ + OH–
H+ + OH+ ⇆ H2O
Neutralization Reaction of Acid and Base
Acids and bases reactions in inorganic chemistry are highly useful in explaining the acid base neutralization in an aqueous solution. When a strong acid HA reacts with strong base BOH in the chemical solution, all are completely dissociating in the solution.
H+ + A– + B+ + OH– ⇆ B+ + A– + H2O
when the above equation balancing by likes ions
H+ + OH– ⇆ H2O
Neutralization Properties of Strong Acids Bases
The heat of neutralization is the heat change associated with the neutralization of 1-gm equivalent acid by 1-gm equivalent alkali in their very dilute solution. Dilute concentration is used in order to avoid any heat change due to the mixing of acid and base. Neutralization is an equilibrium chemical reaction and exothermic reaction. The heat of neutralization of strong acid and strong base is found to constant and equal to 13.6 kcal.
H+ + OH– ⇆ H2O + 13.6 kcal
Since the neutralization of all strong acids and bases reduces to the formation of 1-mole water from hydrogen and hydroxyl ion and thermodynamics enthalpy change (ΔH) will also be the same. The specific heat release during neutralization HCl, HClO4, HNO3, HBr, HI, and H2SO4 and strong base NaOH, KOH, RbOH, and Ca(OH)2), namely 13.4 kcal/mole or 56 KJ/mole.
Limitations of Arrhenius Acid and Base
- According to Arrhenius’s definitions, HCl regarded as an acid when dissolved in water. But if we use organic solvent or gases, HCl does not consider as an acid.
- Arrhenius limitations cannot account for the properties of acid base reaction in non-aqueous solvents. For example, NH4NO3 in liquid ammonia is an acid, though it does not give H+ ions.
- The neutralization examples of acid-base limited to those reactions which can occur in aqueous solutions only. Although the reactions involving salt formation do occur in many other solvents and even in the absence of solvents.
- This theory cannot explain the acidic character of certain salts such as AlCl3 in aqueous solution.
Acids Bases Properties in Water and Ammonia
- Water solution has both acidic and basic nature and it dissociates H+ and OH– ions. But H+ ion readily polarization by other anion or molecule which exists in the solution. Therefore, according to solvent chemistry, all those polar compounds have nature to give H3O+ ions in H2O will act as acids and all those compounds which can give OH– ions in H2O will act as a base.
- NH3 dissociates into two oppositely charged ions which are NH4+ and NH2–. Therefore, all those polar compounds have properties to give NH4+ ions in liquid ammonia will act as acids but all those compounds which can give NH2– ions in liquid ammonia act as bases.
Solvent System Concepts of Acids and Bases
The protonic definition of acids and bases given by Bronsted can be extended to the chemical reaction occurring in non-aqueous solvents containing the hydrogen atoms such as ammonia, hydrogen fluoride, sulfuric acid, acetic acid, hydrogen cyanide, and organic alcohol.
- An acid is a substance which by dissociation in the solvent forms the same cation as does the solvent itself due to auto-ionization.
- A base is one that, gives on dissociation in the solvent the same anion as does the solvent itself on its ionization.
Acid Base Neutralization Reaction Examples
Just as with the Arrhenius acid base properties, neutralization reaction produces salt and solvent. Some examples of neutralization reaction of acid base in chemistry given below
NH4Cl + KNH2 ⇆ KCl + NH3
SOBr2 + K2SO3 ⇆ 2KBr + 2SO2
NOCl + AgNO3 ⇆ AgCl + N2O4
HBr + KOH ⇆ KBr + H2O
Limitations of Solvent Theory
- This theory does not consider the number of acidic and basic properties and reaction which included in the proton affinity of acid.
- The solvent system theory explains acidic and basic nature to the solution only. Therefore, the acids and bases properties in the solid or gaseous state do not explain by this theory.
- It can not explain the neutralization reactions and properties of acids and bases occurring without the presence of ions in the solution of acid chemistry. Therefore, this theory simply said to be an extension of the Arrhenius water-ion concept.