[Chemistry Class Notes] Non – Aqueous Titration Pdf for Exam

Water can behave as a weak acid and a weak base. If we are titrating a very weak acid or weak base in an aqueous solution, then it is possible that it can compete with weak acid or base with regard to proton donation and acceptance. 

Non-Aqueous Titration Theory Example 

[H_{3}O^{+}]  can compete with [RNH{_{3}}^{+}]. If it happens then we don’t get the correct endpoint by titration. A general rule is that acids with[pK_{a}>7] and bases with [pK_{a}>7] cannot be determined accurately in an aqueous solution. So, for titration of weak acids or bases, we use non-aqueous solvents. Many organic solvents such as acetone, alcohol, etc. can easily replace water as they compete less effectively with analytes for proton donation or acceptance. Reactions which occur in non-aqueous titrations can be explained by Bronsted -Lowry theory and its definition of acids and bases. 

Types of Non-Aqueous Solvents Used in Non-Aqueous Titration 

Following four types of solvents are used to dissolve analytes in non-aqueous titrations –

1. Aprotic Solvents 

2. Protophilic Solvents 

3. Protogenic Solvents 

4. Amphiprotic Solvents 

• Aprotic Solvents– These are chemically inert substances such as benzene, chloroform, etc. these are added to ionizing substances to depress solvolysis of the neutralization product which in result sharpening the endpoint.   Examples – benzene, toluene, carbon tetrachloride, etc. 

• Protophilic Solvents– These are basic in nature and react with acids to form solvated protons. A strong protophilic solvent changes the weak acids to strong acids. 

Examples– liquid ammonia, amines, ether, etc. 

Examples- sulfuric acid, formic acid, etc. 

• Amphiprotic Solvents– These solvents have properties of both protophilic and protogenic solvents. Examples – alcohol, acetic acid, etc. 

 

Advantages of Non-aqueous Titrations  

Non-aqueous titration has the following advantages – 

• It is useful for the titrations of very weak acids or bases. 

• Many organic acids which are not soluble in water, can be dissolved in non-aqueous solvents. Thus, titration of these organic acids is very easy. 

• It can be used for titration of mixtures of acids as well. 

• These titrations show sharp end points with internal indicators. 

• It is a simple, qualitative, and selective method. 

• It is a highly accurate method. 

• Preferably non-aqueous titration is used for biological matters. 

• It is very important in pharmacopoeial assays. 

Applications of Non-aqueous Titration 

Non-aqueous titration has various uses in numerous fields. Especially in the field of medicine, non-aqueous titration is very useful. We have listed here a few applications of non-aqueous titration – 

• Non–aqueous titration is used to know the purity of assays. 

• It is used for the determination of concentration expressions. 

• It is used in the determination of hydrophobic compounds, phenobarbitone, diuretics, steroids.

• It is used in the determination of the composition of antitubercular drugs and adrenergic drugs. 

 

Disadvantages of Non-aqueous Titration 

Non–aqueous titration has the following disadvantages – 

• Solvents used in non-aqueous titration are not stable compared to aqueous solvents. 

• In a non-aqueous titration, non-aqueous solvents are required calibration after every use. 

• In non-aqueous titrations temperature corrections are necessary. 

If you want to know more about titration then go through the articles Mohr salt titration with [KMnO_{4}] precipitation titration, oxalic acid titration with [KMNO_{4}], etc. available on . You can register yourself on or download the learning app for more such articles, NCERT Solutions, study material, mock tests, etc.