Factors affecting the degree of ionization:
(a) Temperature - With the rise in temperature, the degree of dissociation of an electrolyte in solution increased. Thus, Degree of dissociation α Temperature
(b) Dilution : On the increasing of dilution, the degree of dissociation increases. But at infinite dilution, their is no effect on the degree of dissociation.
(c) Concentration of the solution :
Degree of dissociation ∝ 1/conc. of the sol. ∝ 1/amount of solute in given vol. ∝ Amount of solvent
(d) Nature of Solvent : Higher the dielectric constant of a solvent, more is its dissociation power or ionising power. Thus ,
Degree of ionisation or dissociation of an electrolyte ∝ dielectric constant of solvent.
Dielectric constant : The dielectric constant of solvent is a measure of its tendency to weaken the forces of attraction between oppositely charged ions of the given electrolyte or the force of attraction applied by solvent molecules on solute molecule is defined as Dielectric constant of solvent.
Note : Water is the most powerful ionizing solvent as its dielectric constant is highest.
(e) Presence of Common Ion : In the presence of a strong electrolyte having common ion, the degree of dissociation of an electrolyte decreases. eg. Ionisation of CH3COOH is suppressed in the presence of HCl due to common H ions.
(f) Nature of Electrolyte : At constant temperature, electrolytes ionize to a different extent in their solutions of same concentration.
Bronsted and lowry concept of acids & bases :
(1) Acid - Proton (H+ ) donor
(2) Base - Proton (H+ ) acceptor
HCl(aq) + H2O(l) H3O+ (aq) + Cl-(aq)
Acid Base ;
HCl(aq) + NH3(aq) NH4+ (aq) + Cl-(aq)
HCl(aq) + CH3COOH(aq) CH3COOH+2(aq)
Acid Base Cl-(aq);
Note :- Here CH3COOH has a less tendency to donate H than HCl, therefore CH3COOH acts as a weak base.