Quantitative analysis deals with the determination of the quantity of the substance to be analyzed. Methods of quantitative analysis may be classified into:
Gravimetric analysis: It depends on isolating and weighing of the final product with known pure, stable and definite form.
Instrumental analysis: It depends on measuring some physical properties which change quantitatively with changing concentration of sample.
Volumetric analysis (Titration): It depends on measuring volume of standard solution (titrant) used for complete reaction with the sample
Titration is the capacity of the sample to combine with the suitable standard quantitatively through quantitative reaction. A quantitative reaction is the reaction that proceeds forward to produce stable product(s) such as weakly ionizable compounds, e.g. H2O, weak acids & base, sparingly soluble salts (precipitate), complex ion, etc. The types of quantitative Reactions can be:
- Neutralization Reactions.
- H2O formation.
- Displacement: Formation of weak acid or weak base.
- Complexometric reactions.
- Redox reactions (Electron transfer).
- Preciptimetric reactions.
Any sample is a solution of unknown concentration and a Standard is a solution of exactly known concentration. The requirements of titrimetric reactions are:
- The reaction must be simple and expressed by a chemical equation.
- A single reaction must occur between the sample and titrant.
- The reaction must be instantaneous (rapid).
- Suitable standard solutions must be available.
- The end point should be easily detected.
Oxidation is loss of electrons and increase in valency number, gain of oxygen or loss of hydrogen:
Fe2+ →Fe3+ + e-1
Reduction is gain of electrons and reduction in valency number, loss of oxygen or gain of hydrogen:
Fe3+ + e-1→Fe2+ , Fe2+ + 2e-1 → Fe0
Oxidizing agent or oxidant is the substance that gain electrons:
Ex: KMnO4, K2Cr2O7, Ce(SO4)2
Reducing agent or reductant is the substance that donate (lose) electrons:
FeSO4, Na2S2O3, H2C2O4
