OCR Analytical Chemistry Section 3 PDF

ANALYTICAL CHEMISTRY SECTION 3 For clinical students. A- Neutralization reaction(acid base titration)  PH INDICATORS indicator Phenolphthalein Methyl orang Color in acidic colorless Red solution Color in pink yello...

ANALYTICAL CHEMISTRY SECTION 3 For clinical students. A- Neutralization reaction(acid base titration)  PH INDICATORS indicator Phenolphthalein Methyl orang Color in acidic colorless Red solution Color in pink yellow basic solution  STANDARD SOLUTIONS Are solutions of exactly known concentration and are very important in volumetric analysis  TYPES OF STANDARD SOLUTION standard primary secondary  PRIMARY STANDARD Def: A high purity compound used to prepare our standard solution Properties of primary standard 1-high purity. 2- Be easily to be tested for impurities. 3-stable in air and solution. 4-not hydroscopic. 5-inexpensive. 6-large formula wieght. 7-soulbe in different solvents.  PRIMARY STANDARD SOLUTION 1-react rapidly with analyte 2-react completely with analyte 3-have long term stability Example: sod carbonate  SECONDARY STANDARD A solution standardized by primary standard As HCl NaOH Used when primary standard unavailable It’s a solution used instead of primary standard in case that it is hard to get the primary standard solution but must be standardized against the primary solution to ensure its concentration is equal to that of primary.  ACID BASE TITRATION Aqueous titration Non aqueous titration  ACID BASE TITRATION I. Aqueous Titrations: Preparation of secondary standard solution A-Preparation 0.1N HCl (36.46) 1- 5ml of pure conc HCl added to 200 ml distilled water in 500 ml conical flask 2-complete to the mark with distilled water  B-STANDARDIZATION WITH 0.1N NA­2­CO3 preparation of primary standard soiution prepare 0.1NNa­2­CO3 (M.Wt= 106) By dissolving 1.325g of Na­2­CO3 in small beaker Then transfer it into 250 ml conical flask then complete to the mark with distilled water  TITRATION 1-10 ml of sample ( primary standard solution ) in conical flask 2-add 2-3 drops of methyl orange 3- titrate with 0.1N HCl 4- end point color changed from yellow to red N1V1=N­2V2 N1 HCl=V2N2/N1 METHYL ORANGE METHYL ORANGE  STANDARDIZATION Calculation of standardization factor : If 10 ml of sod carbonate take 9 ml of HCl then the preparation is concentrated Each 9 ml of HCl need 1 ml water If 10 ml of sod carbonate take 11 ml then the HCl preparation is diluted 10 ml of HCl contain 1 ml excess water  STANDARDIZATION FACTOR ( f) Standardization factor (f) : How much of exact is present in the approximate it ranges from 0.95 to 1.05 out of that range is not of expected strength f= Volume of exact standard Volume of approximate standard OR use correlation of the concentration ??????????