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Acids, Bases And Salts - Theories
Amphoteric : Substances which can act as acid as will as base are known as amphoteric
HCl + H2O
H3O+ + Cl–
base
NH3 + H2O NH4+ + OH–
acidAmphiprotic : An amphiprotic molecule (or ion) can either donate or accept a proton, thus acting either as an acid or a base. Water, amino acids, hydrogen carbonate ions and hydrogen sulfate ions are common examples of amphiprotic species. Since they can donate a proton, all amphiprotic substances contain a hydrogen atom.
Ex.H2O + S2– \( \rightleftharpoons \) OH– + HS–
H2O + HSO4– \( \rightleftharpoons \) H3O+(aq) + SO42–(aq)
According to this concept, neutralisation is a process of transfer of a proton from an acid to a base.
A) CH3COOH + NH3 \( \rightleftharpoons \) NH4+ + CH3COO–
B) NH4+ + S2– \( \rightleftharpoons \) HS– + NH3
C) [Fe(H2O)6]3+ + H2O \( \rightleftharpoons \) H3O+ + [Fe(H2O)5(OH)]2+
An acid–base reaction always proceeds in the direction of formation of the weak acid and the weak base. In the equilibrium,
HA + H2O \( \rightleftharpoons \) H3O+ + A–
Strong acid Strong base Weak acid Weak base
In general "The conjugate base of a strong acid is always a weak base and the conjugate base of a weak acid is always a strong base."
A number of organic compounds containing oxygen, can accept protons and thus act as bases.
Ex. A) C2H5 + H2SO4 \( \rightleftharpoons \) C2H5H2 + HSO4–
Ethanol (Oxonium ion)
B) (C2H5)2+ HCl \( \rightleftharpoons \) (C2H5)2H + Cl–
Ethylether Oxonium ion
Bronsted lowery concept does not differ appreciably from the Arrhenius theory for aqueous solution only.
Autoionisation or Autoprotolysis or Self ionisation
H2O + H2O \( \to \) H3O+ + OH–
acid base
NH3 + NH3 \( \to \) NH4+ + NH2–
acid base
H2SO4 + H2SO4 \( \to \) H3SO4+ + HSO4–
acid base -
Acids, Bases And Salts - Theories
Amphoteric : Substances which can act as acid as will as base are known as amphoteric
HCl + H2O \(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\) H3O+ + Cl–
base
NH3 + H2O \(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\) NH4+ + OH–
acidAmphiprotic : An amphiprotic molecule (or ion) can either donate or accept a proton, thus acting either as an acid or a base. Water, amino acids, hydrogen carbonate ions and hydrogen sulfate ions are common examples of amphiprotic species. Since they can donate a proton, all amphiprotic substances contain a hydrogen atom.
Ex.H2O + S2– \( \rightleftharpoons \) OH– + HS–
H2O + HSO4– \( \rightleftharpoons \) H3O+(aq) + SO42–(aq)
According to this concept, neutralisation is a process of transfer of a proton from an acid to a base.
A) CH3COOH + NH3 \( \rightleftharpoons \) NH4+ + CH3COO–
B) NH4+ + S2– \( \rightleftharpoons \) HS– + NH3
C) [Fe(H2O)6]3+ + H2O \( \rightleftharpoons \) H3O+ + [Fe(H2O)5(OH)]2+
An acid–base reaction always proceeds in the direction of formation of the weak acid and the weak base. In the equilibrium,
HA + H2O \( \rightleftharpoons \) H3O+ + A–
Strong acid Strong base Weak acid Weak base
In general "The conjugate base of a strong acid is always a weak base and the conjugate base of a weak acid is always a strong base."
A number of organic compounds containing oxygen, can accept protons and thus act as bases.
Ex. A) C2H5 + H2SO4 \( \rightleftharpoons \) C2H5H2 + HSO4–
Ethanol (Oxonium ion)
B) (C2H5)2+ HCl \( \rightleftharpoons \) (C2H5)2H + Cl–
Ethylether Oxonium ion
Bronsted lowery concept does not differ appreciably from the Arrhenius theory for aqueous solution only.
Autoionisation or Autoprotolysis or Self ionisation
H2O + H2O \( \to \) H3O+ + OH–
acid base
NH3 + NH3 \( \to \) NH4+ + NH2–
acid base
H2SO4 + H2SO4 \( \to \) H3SO4+ + HSO4–
acid base