NON-AQUEOUS TITRATIONS: Definition, Advantage, Solvent Types and MCQ

 DEFINITION :-

Non-aqueous titration is the titration of substance dissolved in solvent other than water.

OR

Non-aqueous titrations are those in which the titration of weakly acidic or basic substances are carried out using non-aqueous solvents so as to get sharp end point.

ADVANTAGE OF NON-AQUEOUS TITRATIONS:-

• Organic acids or bases that are insoluble in water are soluble in non-aqueous.
• Organic acids which is of comparable strength to water can be titrated easily in non-aqueous solvent.

DIS-ADVANTAGE OF NON-AQUEOUS TITRATIONS:-

• temp.,moisture,CO2,should be control.
• solvent are expensive.
• volatile solvent can polute environment.
• Indicator must be prepare in non-aqueous medium.

BRONSTED-LOWRY CONCEPT FOR ACID-BASE :-

ACID :- Acid is a proton donor.

BASE:- Base is a proton acceptor.

TYPES OF SOLVENTS 

1. Aprotic solvent :- aprotic solvents include those substance which may be considered chemically neutral and virtually un-reactive under the condition empolyed. carbon tetrachloride and toluene come in this group they possess low dielectric constant,do not cause ionization in solute and do not causes ionization in solute and do not undergo reactions with acid and bases. Aprotic solvents are frequently used to dilute reaction mixture. Neither accepts nor donates protons. eg. CHCL3,C6H6,CCL4 etc.
2. Protogenic solvents :- They are acidic substance & exert a levelling effect on bases. eg. HCL,H2SO4 etc.
3. Protophilic solvents :- They are basic & react with acid to from solvated protons. eg.NaOH,KOH etc
4. Amphoteric :- Act both as acid or base eg. H2O,HAC etc.

WATER INTERFERENCE IN NON AQUEOUS TITRATIONS:-

Non-aqueous titration mainly carried out between weakly acidc & weakly basic substance.

Weak acid & weak base in aqueous solutions.eg. in presence of H2O. Here water due to its amphiprotic nature it act as a strong acid and the titration takes place between strong acid & weak base.so the exact end point can not be found properly.

BASIC PRINCIPAL OF NON AQUEOUS TITRATIONS :-

FORMATION OF ONIUM ION :-

CH₃COOH   CH₃COO^—  H⁺

^HCLO₄        ClO₄^–  H⁺

^CH₃ ^COOH₂^{+      ClO}₄^–

The titration of weak bases are done with HClO4 in acetic acid because in presence of HClo4 acetic acid reacts with HClO4 and produced onium ion which act a strong acid so that the titration takes place between strong acid& weak base.

MCQ :-

1. Which is not a disadvantage of Non – aqueous Titration ?

A.Volatile solvent can polute environment

B.Solvent are expensive.

C.Indicator must be prepare in non-aqueous medium.

D.Organic acids which is of comparable strength to water can be titrated easily in non-aqueous solvent.

2. Which is example of aprotic solvent ?

A. H2SO4

B. KOH

C. HAC

D. Benzene

3. Which is example of Protogenic solvents ?

A. H2SO4

B. KOH

C. HAC

D. Benzene

4. Which compound is Titration are carried out by non aqueous Titration ?

A. Organic acids

B. Organic bases

C. A and B

D. None of the above

5.Which is example of  Protophilic solvent ?

A. H2SO4

B. KOH

C. HAC

D. Benzene

6.Which is example of Amphoteric solvents ?

A. H2SO4

B. KOH

C. HAC

D. Benzene

7. Amphoteric means

A. Acidic nature

B. Basic nature

C. Neutral

D. A and B

Answer key :-

1. D

2. D

3. A

4. C

5. B

6. C

7. D

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REFERENCE :- 

TEXT BOOK OF PHARMACEUTICAL ANALYSIS THIRD EDITIONS BY DR.S.RAVI SANKAR (PG.NO.19.1 TO 19.12)