Analytical Chemistry Lecture Notes PDF

Neutralization reactions Acid Base Titration By Prof. Dr. Hytham M. Ahmed Assoc. Prof. Dr. Hytham M. Ahmed 0  Analytical Chemistry Qualitative Analysis Quantitative Analysis Assoc. Prof. Dr. Hytham M. Ahmed 0 The qualitative analysis detects a...

Neutralization reactions Acid Base Titration By Prof. Dr. Hytham M. Ahmed Assoc. Prof. Dr. Hytham M. Ahmed 0  Analytical Chemistry Qualitative Analysis Quantitative Analysis Assoc. Prof. Dr. Hytham M. Ahmed 0 The qualitative analysis detects and identifies the constituents of a compound or a mixture of compounds or elements. The quantitative analysis determines the quantity, and the purity of the sample. Assoc. Prof. Dr. Hytham M. Ahmed 0  Methods used in Quantitative Analysis These are classified on the basis of 1) the sample concentration: Macro quantities of 100 mg or more. Semi-micro quantities ranging from 10 to 100 mg. Micro quantities not exceeding 1 mg. 2) The kind of the analyzed material, e.g. food analysis, water analysis, etc 3) The process of the final measurement. Assoc. Prof. Dr. Hytham M. Ahmed 0  Classification on the basis of the process of final measurement: a) Volumetric or Titrimetric Analysis b) Gravimetric Analysis (quantitative analysis by weight) c) Physicochemical or Instrumental Methods of Analysis Assoc. Prof. Dr. Hytham M. Ahmed 0 a) Volumetric or Titrimetric Analysis It depends on measuring the volume of both the analyzed sample and the standard solution needed for complete reaction with this sample The term titration means measurement of the capacity of a sample to combine with a known standard reagent in a quantitative manner. 'Titrant' is the compound in the titration buret, its concentration is exactly known. 'Titrand' is the substance which is being analysed in the titration. Assoc. Prof. Dr. Hytham M. Ahmed 0 b) Gravimetric Analysis (quantitative analysis by weight) It is the process of isolating and weighing a final product with a known, pure, stable and definite chemical structure. Assoc. Prof. Dr. Hytham M. Ahmed 0 c) Physicochemical or Instrumental Methods of Analysis It depends on measuring some physical properties that is quantitatively related to the concentration of the constituent to be analyzed. It requires certain instruments, that is why it is called instrumental analysis. Assoc. Prof. Dr. Hytham M. Ahmed 0  Volumetric or Titrimetric Analysis Assoc. Prof. Dr. Hytham M. Ahmed 0  Types of Reactions Used in Volumetric Analysis 1. Ionic combination reactions: Depend on the formation of slightly ionized or slightly soluble products. It includes: 1) Neutralization reactions :- H+ + OH- H2O “ very slightly ionized” 2) Precipitation reactions :- Ag+ + Cl- AgCl Ba 2+ + SO42- BaSO4 3) Complexation reactions. Ag+ + 2CN- [Ag(CN)2]- “weakly ionized” Ca2+ + H2Y2- 2H+ + CaY2- Assoc. Prof. Dr. Hytham M. Ahmed 0 2. Electron transfer reactions (Redox) : These reactions involve transfer of electrons Ce4+ + Fe2+ Ce3+ + Fe3+ Assoc. Prof. Dr. Hytham M. Ahmed 0 Requirements Of Titrimetric Reactions Assoc. Prof. Dr. Hytham M. Ahmed 0  Requirements of titrimetric reactions: 1)The reaction must be simple and can be expressed by a chemical equation. 2)A single reaction must occur between the desired constituent and the titrant i.e. no side reactions. 3)The reaction must be instantaneous, or a catalyst is used. 4)A suitable standard solution must be available as a titrant. 5)The end point of the reaction should be easily detected; either by some change in the physical or chemical properties of the solution, or by the use of an indicator. Assoc. Prof. Dr. Hytham M. Ahmed 0  Standard Solutions: They are solutions of exact and known chemical composition and concentration. Molar Solution: It is a solution of known concentration, each liter of which contain one gram molecular weight.e.g. M NaOH, M Na2CO3 Assoc. Prof. Dr. Hytham M. Ahmed 0  Preparation of Standard Solutions a) Direct Methods: Accurately weighed amount of primary standard is dissolved and made up to the required volume in a volumetric flask. b) Indirect Methods:[secondary standard] If the solute is not a primary standard, it is used to prepare solutions of approximate concentrations, which are subsequently standardized against a solution of a primary standard. Assoc. Prof. Dr. Hytham M. Ahmed 0  What are the characteristics of a good primary standard? 1)Easily obtained in a very high grade of purity and of known composition “A.R.” analytical reagent grade. 2)Easily tested for impurities by simple tests. 3)Stable, non-hygroscopic (to minimize weight changes due to humidity), non-efflorescent [deos not lose water of crystallization], non-volatile and can be dried at “110-120◦C” without decomposition. 4)Reacts quantitatively according to a balanced chemical equation “stoichiometrically” 5)Readily soluble in the solvent used. 6)Have high equivalent weights to minimize weighing errors Assoc. Prof. Dr. Hytham M. Ahmed 0 Examples of primary standards used in acid-base reactions are : 1. Potassium acid phthalate 2. Constant-boiling-point HCl 3. Anhydrous Na2CO3 4. Benzoic acid 5. Mercuric oxide 6. Potassium bicarbonate Assoc. Prof. Dr. Hytham M. Ahmed 0 Examples of primary standards 1. Acid-Base reactions: Na2CO3, Na2B4O7(Sodium tetrabromate), KH(C8H404) (Potassium hydrogen phthalate), KH(I03)2 (Potassium hydrogen iodate), HCl, C6H5COOH (Benzoic acid). Assoc. Prof. Dr. Hytham M. Ahmed 0 Examples of primary standards 2. Complex formation reactions: Ag, AgNO3, NaCl, Various metals (pure Zn, Mg, Cu, Mn) and their salts. 3.Precipitation reactions: Ag, AgNO3, NaCl, KCl, KBr. Assoc. Prof. Dr. Hytham M. Ahmed 0  Examples of primary standards 4.Oxidation-reduction reactions: K2Cr2O7, KbrO3 (Potassium borate), KIO3, KH(IO3)2 (Potassium hydrogen iodate), Sodium Oxalate (Na2C2O4), Arsenic (‫ )׀׀׀‬oxide(As2O3) Assoc. Prof. Dr. Hytham M. Ahmed 0