CHEMICAL ANALYSIS BY Dr.JAGADEESH

CHEMICAL ANALYSIS RESOLVING A SAMPLE IN TO ITS ULTIMATE COMPONENTS ( COMPOUNDS OR ELEMENTS)

IMPORTANCE OF CHEMICAL ANALYSIS IN INDUSTRY: TO CHECK THE QUALITY OF RAW MATERIAL AND FINISHED PRODUCTS IN MEDICINE: TO DIAGNOSE THE DISEASES IN FOOD AND AGRICULTURE: TO CHECK THE TOXIC MATERIALS IN ENVIRONMENTAL SCIENCE: TO MEASURE THE POLLUTANTS IN AIR, WATER AND SOIL

TYPES OF CHEMICAL ANALYSIS QUALITATIVE: IT FINDS OUT THE NATURE OF ELEMENTS OR COMPOUNDS (IDENTIFIES WHAT IS INSIDE THE SAMPLE) QUANTITATIVE : IT ESTIMATES THE CONCENTRATION OF THE ELEMENTS OR COMPOUNDS PRESENT IN A SAMPLE ( FINDS OUT HOW MUCH?)

METHODS OF CHEMICAL ANALYSIS VOLUMETRIC ANALYSIS ( Involves the measurement of volume of reacting solutions) GRAVIMETRIC ANALYSIS (Involves the measurement of the weight of a precipitate) SPECTROSCOPIC ANALYSIS ( Involves the measurement of light absorbed or transmitted ) e.g. Visible, UV, Infra-red Spectroscopy and Atomic Absorption Spectroscopy ( Depending on the nature of light and the source used) Electro-chemical methods : ( Potentiometry, Voltammetry, Coulometry) Involves the measurement of potential, Current-Voltage variation, total electrical Charge passed through the solution etc.

VOLUMETRIC ANALYSIS It measures the volume of a solution of known / unknown concentration reacted with a definite volume of another solution of unknown / known.

VOLUMETRIC ANALYSIS Also known as Titrimetric analysis. Important terms: Standard Solution: (Titrant )A solution of Known Concentration Titrand : Solution of unknown Concentration Titration: Process of adding small quantities of a solution to the other to find the equivalence point. Equivalence point: The point at which the reaction between the titrant and titrand is complete. Indicator: A reagent used to detect the end point by some physical change produced by it ( like a colour change)

Essential conditions Simple reaction must be possible between the two solutions and the completion of it in stoichiometric proportions. Reaction must be fast. A marked change should be occurring at the end point. An indicator must be available to detect the end point.

Classification On the basis of the type of reaction: Acid- Base titration ( Acidimetry or Alkalimetry) Precipitation titration Complexometric titration Oxidation- reduction titration

Terms Standard Solution The strength of solution is expressed by i) Molarity ii) Normality iii) Molality iv) Mole fraction v) Percentage.

Calculation of Equivalent weight Equivalent Weight of an Acid Basicity of an acid Equivalent Weight of a base Acidity of a base Equivalent of a salt Equivalent Weight of an Oxidizing agent Equivalent Weight of a Reducing agent

Preparation of Standard Solutions Weigh definite quantity of Pure Substance. Dissolve in suitable solvent. Dilute and prepare required strength. V 1 M 1 =V 2 M 2 Pure substances: e.g. Sodium carbonate, Potassium hydrogen phthalate, benzoic acid, Sodium tetraborate, Silver nitrate, Sodium chloride, Potassium chloride, Potassium dichromate etc. Secondary standards-indirect method.

Primary & Secondary Standards Conditions to be satisfied by Primary standard. Must be easy to get in pure form, to dry and preserve in pure state. Must be unaltered in air ( must not be hygroscopic, efflorescent or Deliquescent and also not affected by Oxygen or Carbon dioxide) Impurities should not exceed 0.01 to 0.02% and should be able to be analyzed. High relative molecular mass for the compound. Error in weighing should not effect the accuracy of the strength of solution Substance should be readily soluble. Reaction must be stoichiometrically valid and fast