Hello friends, 

This chapter in physical and inorganic chemistry deals with the study of solutions, solute, solvent and an equilibrium which exists between ions and unionized molecules of weak electrolyte solutions. Like chemical equilibrium, ionic equilibrium is dynamic in nature. 

According to Arrhenius theory, an acid is a substance which contains hydrogen and on dissolving in water produces hydrogen ions. Similarly, base is a substance which contains OH group and on dissolving in water produces hydroxyl ions. Neutralisation is the reaction in which and acid reacts with base to produce salt and water in their aqueous solutions. 

The more general Bronsted – Lowry theory defined an acid as a proton donor and a base as proton acceptor and acid-base reaction as a proton transfer reaction. Conjugate acid base pair is an acid base pair in which acid and base are formed from each other by loss and gain of proton. Water has dual nature, it can accept a proton from an acid and acts as a base. It can also donate a proton to a base and acts as an acid. 

Lewis generalized the definition of acids and bases on the basis of electron pair donor or acceptor. Acid is electron pair acceptor while base is electron pair donor. 

The conduction of electricity through aqueous solution of acids, bases and salts is due to anions and cations produced by dissociation of electrolyte in aqueous solution. There exists an equilibrium between the ions and unionized electrolyte molecules in case of weak electrolytes. The strong electrolytes are almost completely dissociated in their aqueous solutions where as weak acids, weak bases are feebly dissociated. 

Ionic product of water is a modified equilibrium constant obtained by applying the mass law equation to ionization equilibrium of water, assuming concentration of undissociated water as constant at equilibrium. The ionic product of water is given by K w = [H+] ×[OH-]. It has a value of 1 ×10-14 at 298 K.

Sorensen developed pH scale to explain the acidic, basic or neutral nature of solution, where pH =-log10 [H+].  

    For acidic solution, pH<7, for basic solution, ph>7 and for any neutral solution, pH = 7. 

The product of concentration of ions of sparingly soluble electrolyte in its saturated solution at a given temperature is constant and it is called as solubility product K sp. Solubility product has application in prediction of precipitation and qualitative analysis of basic radicals. 

The dissociation of a weak electrolyte and solubility of a salt is suppressed by the addition of a strong electrolyte containing a common ion. This is known as common ion effect. The principle of common ion effect is useful in purification of common salt and salting out of soap. 

The solution which resists sudden change in pH due to addition of small amount of strong acid or strong base is called a buffer solution. Buffer solutions are of three types acidic, basic and single salt buffer solution. 

Hydrolysis is a reaction of a salt with water forming acid and base i.e. reverse of neutralistion. It is a process in which the cations or anions or both the ions of a salt react with water producing acidic or basic or neutral solution depending on the type of salt. Aqueous solutions of salts may be acidic, basic or neutral, depending on the strengths of acid and base formed on hydrolysis. The nature of solution depends on K a, K b values. 

 

Tags

• MHT-CET
• AIEEE