Properties of Acid and Base in Chemistry
Properties of acids and bases are opposite in nature to each other in the chemical reaction. According to Arrhenius’s acid base definitions in chemistry, acids dissociate hydrogen ion whereas bases hydroxyl ion in water solution. But due to limitations, we can not explain acidic and basic properties and the nature of acids bases neutralization reaction by only one theory for study chemistry. For example, hydrogen chloride or hydrochloric acid shows acidic properties only when it dissolved in water solution but if we use benzene or gaseous state, it does not consider as an acid according to Arrhenius.
But acids and bases are the following common properties
- Acids are the chemical substances whose aqueous solution is sour in nature and turns blue litmus to red.
- Bases are the substance 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 and definitions of acids and bases reaction we need to know about five theory
- Arrhenius acids and bases definitions
- Acids and bases in a solution
- Protonic concept
- Lewis definitions
- The 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 chemistry are highly useful in explaining the acid base neutralization in an aqueous solution.
Where HA and BOH are strong acid and base solution and completely dissociate.
H+ + A– + B+ + OH– ⇆ B+ + A– + H2O
Thus canceling by likes ions
H+ + OH– ⇆ H2O
Neutralization Reaction in Water
The neutralization reaction of all strong acids and bases used to the formation of 1-mole water from hydrogen ion and hydroxyl ion. Thus the thermodynamics enthalpy change (ΔH) will also be the same for all the acidic and basic reactions between strong acids and bases solution.
H+ + OH– ⇆ H2O + 13.6 kcal
Therefore, 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 is an acid only when it dissolved in water. But if we use solvent such as benzene or when it exists in the gaseous state, it 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.
Similarly, many organic compounds in NH3, which do not give OH– ions at all, actually known to show basic character.
- 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.
Acidic and Basic Nature of Water
Protic solvent dissociates into two oppositely charged ions. For example, water solution has both acidic and basic nature and it dissociates H+ and OH– ions.
H2O ⇆ H+ + OH–
But H+ ion readily polarizes other anion or molecule which exists in the solution. So overall dissociation reaction of the solvent
H2O + H2O ⇆ H3O+ + OH–
Thus according to solvent chemistry, all those 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.
Acids and Bases Properties in Liquid Ammonia
NH3 dissociates into two oppositely charged ions which are NH4+ and NH2–.
NH3 + NH3 ⇆ NH4+ + NH2–
Therefore, those 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.
Properties of Acid and Base in the Solution
The dissociation of non-aqueous solvents directly responsible for the nature of the basic reaction that can be initiated in such solvents. Thus according to the solvent system concept
- 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.
Examples of Acid Base Neutralization
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
|Solvent||Acids and bases reaction|
|NH3||NH4Cl + KNH2 ⇆ KCl + NH3|
|SO2||SOBr2 + K2SO3 ⇆ 2KBr + 2SO2|
|NOCl||NOCl + AgNO3 ⇆ AgCl + N2O4|
|H2O||HBr + KOH ⇆ KBr + H2O|
Limitations of Solvent Theory
- Solvent system definitions do not include acidic and basic properties of acids and bases in the solid and gaseous state.
- Due to the limitations of the solvent system theory, we do not explain acidic and basic properties and reactions of acids and bases in the absence of solvent.
- It can not explain acidic and basic properties acids, occurring without the presence of ions in solution.