Chem- IONIC EQUILIBRIUM : 18 min/pg. explain to yourself.
Definition Ionic equilibrium: A state where the rate of ionization of molecules to
form ions equals the rate of combination of ions to form molecules.. Importance:
Critical in reactions involving acids, bases, and salts.
Applications: 1. Buffer solutions: Control pH in living systems, agriculture, and
industries.
2. Solubility equilibrium: Relevant for slightly soluble salts, e.g., calcium
phosphate (Ca₃(PO₄)₂) in bones and teeth.
Electrolytes: Compounds that produce ions when dissolved in water; ions
move freely and conduct electricity.
Strong electrolytes - Electrolytes, when dissolved in water that are almost
completely converted into ions.
Examples: All Ionic compounds: NaCl, KCl, KNO₃, NH₄Cl and Some
covalent compounds: HCl, etc. – strong electrolytes. Ions forming
(dissociation or ionization) is Represented by single arrow (→):
NaCl(aq) → Na⁺(aq) + Cl⁻(aq)
HCl(g) + H₂O(l) → H₃O⁺(aq) + Cl⁻(aq)
Weak electrolytes are electrolytes that ionize only partially. Many covalent
compounds like : CH₃COOH, NH₄OH, C₆H₅NH₂ are weak electrolytes. Such
compounds are present as both unionized molecules and ions.
. This equilibrium between unionized molecules and the ions is represented
by ‘reversible arrows’. For example: CH₃COOH(l) + H₂O(l) ⇌ H₃O⁺(aq) +
CH₃COO⁻(aq)
Degree of Ionization (α):
Fraction or percentage of total amount of electrolytes present in form as ions.
Helps find the extent of ionization for weak electrolytes.
Ionization of Weak Electrolytes
, The weak electrolyte AB dissolves in water and partly splits into ions –
above here ionization of weak electrolyte AB.
Initial concentration (c): = amount of AB before ionization, in mol dm⁻³
, This expression for α is known as Ostwald’s Dilution Law. According to it α,
the degree of ionization of a weak electrolyte depends upon:
(i) temperature (since K depends upon T) (ii) concentration of the
electrolyte, c.
At a constant temperature, α is inversely proportion to the square root of
the concentration. Qualitatively, α increases with the dilution of the
solution.
General Concepts of Acids and Bases
We can define acids and bases based on three different concepts – 1.
Arrhenius
2. Brønsted–Lowry, 3. Lewis
1. Arrhenius Concept- . According to this concept Arrhenius Acid is : A
substance that produces hydrogen ions (H⁺) when dissolved in water.
Definition Ionic equilibrium: A state where the rate of ionization of molecules to
form ions equals the rate of combination of ions to form molecules.. Importance:
Critical in reactions involving acids, bases, and salts.
Applications: 1. Buffer solutions: Control pH in living systems, agriculture, and
industries.
2. Solubility equilibrium: Relevant for slightly soluble salts, e.g., calcium
phosphate (Ca₃(PO₄)₂) in bones and teeth.
Electrolytes: Compounds that produce ions when dissolved in water; ions
move freely and conduct electricity.
Strong electrolytes - Electrolytes, when dissolved in water that are almost
completely converted into ions.
Examples: All Ionic compounds: NaCl, KCl, KNO₃, NH₄Cl and Some
covalent compounds: HCl, etc. – strong electrolytes. Ions forming
(dissociation or ionization) is Represented by single arrow (→):
NaCl(aq) → Na⁺(aq) + Cl⁻(aq)
HCl(g) + H₂O(l) → H₃O⁺(aq) + Cl⁻(aq)
Weak electrolytes are electrolytes that ionize only partially. Many covalent
compounds like : CH₃COOH, NH₄OH, C₆H₅NH₂ are weak electrolytes. Such
compounds are present as both unionized molecules and ions.
. This equilibrium between unionized molecules and the ions is represented
by ‘reversible arrows’. For example: CH₃COOH(l) + H₂O(l) ⇌ H₃O⁺(aq) +
CH₃COO⁻(aq)
Degree of Ionization (α):
Fraction or percentage of total amount of electrolytes present in form as ions.
Helps find the extent of ionization for weak electrolytes.
Ionization of Weak Electrolytes
, The weak electrolyte AB dissolves in water and partly splits into ions –
above here ionization of weak electrolyte AB.
Initial concentration (c): = amount of AB before ionization, in mol dm⁻³
, This expression for α is known as Ostwald’s Dilution Law. According to it α,
the degree of ionization of a weak electrolyte depends upon:
(i) temperature (since K depends upon T) (ii) concentration of the
electrolyte, c.
At a constant temperature, α is inversely proportion to the square root of
the concentration. Qualitatively, α increases with the dilution of the
solution.
General Concepts of Acids and Bases
We can define acids and bases based on three different concepts – 1.
Arrhenius
2. Brønsted–Lowry, 3. Lewis
1. Arrhenius Concept- . According to this concept Arrhenius Acid is : A
substance that produces hydrogen ions (H⁺) when dissolved in water.
