Chemistry > Ionic Equilibrium > 3.0 Arrehenius Theory of Electrolyte Ionization (Dissociation)
Ionic Equilibrium
1.0 Reversible Reaction
2.0 $pH$ Scale
3.0 Arrehenius Theory of Electrolyte Ionization (Dissociation)
4.0 Ionization of Water
5.0 Determination of $pH$ of acids and bases
5.1 Strong acid
5.2 Weak acid
5.3 Strong Acid + Weak Acid
5.4 Two weak acids
5.5 Dibasic and polyprotic weak acids
6.0 Salt Hydrolysis
6.1 Salts of weak acid + strong base
6.2 Salt of weak base + strong acid
6.3 Salt of weak acid and weak base
7.0 Buffer Solution
8.0 Solubility and Solubility Product
3.1 Degree of Ionization (Dissociation)
5.2 Weak acid
5.3 Strong Acid + Weak Acid
5.4 Two weak acids
5.5 Dibasic and polyprotic weak acids
6.2 Salt of weak base + strong acid
6.3 Salt of weak acid and weak base
$\alpha $ is fractional conversion of reactant or $${\text{ }}\alpha {\text{ = }}\frac{{{\text{Moles of reactant dissociated}}}}{{{\text{Initial moles of reactant}}}}$$
The value of $\alpha $ depends on
1. Nature of solute (electrolyte):
Strong electrolyte dissociate completely whereas weak electrolytes dissociate partially.
2. Nature of solvent:
A solvent having high value of dielectric constant and high solvation (in case of water hydration) will favour dissociation.
3. Temperature:
On increasing temperature degree of dissociation increases.
4. Concentration:
For weak electrolytes, degree of dissociation increases by increasing dilution or decreasing concentration (Ostwald’s dilution law).
- Ostwald’s dilution law: Applicable to weak electrolytes (acids or bases)
If $\alpha $ is negligible with respect to $1$ $\left( {\alpha {\text{ < }}{\text{.05}}} \right)$, then for monobasic acid and monoacidic base $${K_C}{\text{ = C}}{\alpha ^2}$$ or $$\alpha {\text{ = }}\sqrt {\frac{{{K_c}}}{C}} {\text{ = }}\sqrt {{K_C}V} $$ where $V$ is the volume of solution. So $$\alpha \propto \frac{1}{{\sqrt C }}\quad {\text{or}}\quad \alpha \propto \sqrt V $$ At infinite dilution $\alpha $ reaches its maximum value i.e., unity.
5. Presence of other solute (Common Ion Effect):
When other substance is also present in water it may affect the $\alpha $ of the weak electrolyte. Degree of ionization of a weak electrolyte is suppressed by addition of a substance having an ion common to weak electrolyte is known as Common ion effect.
