This PPT is about the solvent system definition of acids and bases in inorganic chemistry . This power point is useful to those who study chemistry in college and also useful for University students and also for PhD students

1. 1. Solvent system
definition of acids and
bases
3RD SEM
BY SOURAV PAUL

2. (1)Some Facts
 Acid base properties are closely connected with the properties of solvents.
 Solvent system definition applies in all cases where the solvent is capable of
autoionization whetherprotons are involved or not , i.e aprotic as well as
protic solvent .
 Protic Solvent : protic solvent contains ionizable proton. (Eg- H₂O, HF)
 Aprotic Solvent: aprotic solvent not have any ionizable proton. (Eg-
CCl₄,DMF,DMSO,THF)
 According to the solvent system definition -
1. Acid is a substance that can generate the same cation as does the solvent
itself due to autoionization .
2. Similarly, Base can generate the anion part .

3. (2)Theory of autoionization
 Studies on certain nonaqueous system, reveled that reactions in these solvents may be
explained by assuming auto-ionization of the solvent similar to water :
 Substance furnishing H₃O⁺ ions in water act as acids in aqueous medium
 Substance furnishing NH₃⁺ ion In liquid ammonia behaves as an acid
 Similarly, substance furnishing NH₄⁻ ion in liquid ammonia are similar to those the
compounds giving OH⁻ ion in water.
1. Acids in liquid ammonia –NH₄Cl NH₄NO₃ etc.
2. Bases in liquid ammonia –KNH₂ NaNH₂ etc.

4. Examples of Autoionization
 Other examples :
Autoionization of SO₂:
Acid in SO₂:
SOCl₂ → SO²⁺ + 2Cl⁻
Base in SO₂:
CaSO₃ → Ca²⁺ + 2SO₃²⁻
Neutralization :
SOCl₂ +CaSO₃ → CaCl₂+2SO₂
Geneal Formula of Autoionization
• AB +AB ⇌ A⁺ + AB₂⁻
• EXCEPTION
COCl₂ ⇌ COCl⁺ + Cl⁻
Acid:
AlCl₃+COCl₂ → COCl⁺ + AlCl₄
Base :
COCl₂ → Ca²⁺ + 2Cl⁻
NEUTRALISATION :
2COCl⁺AlCl₄⁻ + CaCl₂→Ca[AlCl₄]₂ + 2CaCO₂

5. (3)Strong and weak acid and bases
 Strong acids dissociates completely into ions in water
 HA (g or l) + H₂O (l) → H₃O⁺ (aq) + A⁻ (aq)
 Weak acids dissociates very slightly into ions in water
HA (aq) + H₂O (l) ⇌ H₃O⁺ (aq) + A⁻ (aq)
 acid dissociation constant
Kc = [H₃O⁺] [A⁻] /[H₂O] [HA]
Kc [H₂O] = Ka = [H₃O⁺] [A⁻] / [HA]
strong acid have higher [H₃O⁺] , larger Ka
weak acid have lower [H₃O⁺] , smaller Ka
**similarly we can also calculate Kb, Kb= [B⁺][OH⁻]/[BOH]

6. (4)Ionic products and nutral points
 For water as a solvent the ionic product is
Kw=[H₃O⁺] ×[OH⁻]
 At 25°C corresponding nutral point is Pᴴ =-log[H⁺]
= - 0.5 log [Kw]
 Ionic product of any solvent AB is
 AB + AB ⇌ A⁺ + AB₂⁻
 K(AB) = [A⁺]×[AB₂⁻]
 The neutral point is P(A) = -0.5 log [Kab] = 0.5 Pᵏᵃ
Ionic products and nutral points of
some non aqueous solvents:

7. (5)Demerits and Relativity of acidic
and basic character of CH₃COOH
 Behavior of CH₃COOH In H₂O NH₃ and HF:
 In water acetic acid behaves as a weak acid,
 In liquid ammonia acetic acid behaves as a strong acid,
 In HF asetic acid behaves as a base .
 Demerits:
1. It places too much emphasis on Autoionization of solvent,
ignoring other physical and chemical properties of solvents.
2. Acid-base reaction occuring in absence of any solvent
cannot define by it.

8. Thank You