(i) When a salt of a weak acid is added to the acid itself, the dissociation of the weak acid is suppressed further.
(ii) For example, the addition of sodium acetate to acetic acid solution leads to the suppression in the dissociation of acetic acid which is already weakly dissociated.
(iii) In this case, CH₃COOH and CH₃COONa have the common ion, CH₃COO^-.

Ostwald's dilution law is applicable only for weak electrolyte and does not hold good for concentrated solution.

FeCl₃ when dissolved in water gives strong acid HCl and a weak base Fe(OH)₃ A strong acid ionises completely so concentration of H⁺ ion becomes much greater than OH^- ion. So, aqueous solution of FeCl₃ is acidic.

Common ion effect decreases the solubility of the electrolyte.

The conjugate base of HF is F^-
For F^-, \({ K }_{ b }=\frac { { K }_{ w } }{ { K }_{ a } } =\frac { { 10 }^{ -14 } }{ { 6.8\times 10 }^{ -14 } } \)
= 1.47 x 10^-11.

pK_w = pH + pOH = 10^-12
For a neutral solution, pH = pOH
So pH = pOH = 6.

According to Lewis concept of Acid and bases, any species capable of accepting an electron pair is an acid. BF₃ is electron deficient so accepts a pair of electron, Hence termed as acid

Magnesium has to precipitate as Mg(OH)₂ when treated with NH₄OH, but addition of NH₄CI will suppress the ionisation of NH₄OH due to common ion effect. So ionic product of Mg²⁺ and OH^- ions will be less than the solubility product (K_sp) of Mg(OH)₂. Hence will not precipitate.

With increase in temperature the ionic product of water will increase since the concentration of H₃O⁺ and OH^- ions will increase.

When the product of molar concentration of the constituent ions i.e., ionic product, exceeds the solubility product then the compound gets precipitated. Ionic product > K_sp, precipitation will occur and the solution is super saturated.

When an acid reacts with a base, a salt and water are formed and the reaction is called neutralization.

(i) Acidic buffer solution: a solution containing a weak acid and its salt.
Example: Solution containing acetic acid and sodium acetate
(ii) Basic buffer solution: a solution containing a weak base and its salt.
Example: Solution containing NH₄OH and NH₄Cl.

Buffer is a solution which consists of a mixture of a weak acid and its conjugate base (or) a weak base and its conjugate acid.

(i) Arrhenius theory does not explain the behaviour of acids and bases in non aqueous solvents such as acetone, Tetrahydrofuran etc ..
(ii) This theory does not account for the basicity of the substances like ammonia (NH₃) which do not possess hydroxyl group.