conductometric titration

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A SEMINAR ON CONDUCTOMETRIC TITRATION:

A SEMINAR ON CONDUCTOMETRIC TITRATION PRESENTED BY- DWIVEDI ASHISH M.PHARM.1 st SEM GUIDED BY-Mr. V.B.JADHAV 1

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2 Contents: 1.Conductometry-: Introduction Ohm’s law. Conductometric measurements . Factor affecting conductivity. Application of conductometry . 2.Conductometric titration-: Introduction. Types of conductometric tiration. Advantages of conductometric tiration. 3.Recent devlopement 4 .References .

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Conductometry means measuring the conductivity of ionic solutions caused by mobility of ions towards respective electrodes in presence of an electric field. Conductivity is measured by using conductometer. Units of conductivity is mhos( Ω -1 ). Conductivity is generally measured by using a Wheatstone bridge circuit and a conductivity cell made of platinum. V-potential difference in volts i-current in amperes 3

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4 Total conductance of the solution is directly proportional to the sum of the n individual ion contributions . G =  c i  m,i

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Ohm’s law- The magnitude of conductometric titration is based on ohm’s law. R where i = current in amperes e = potential difference R = resistance in ohm’s 5

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6 Conductivity measurements Electrodes Two parallel platinized Pt. foil electrodes or Pt. black with electrodeposited a porous Pt. film which increases the surface area of the electrodes and further reduces faradaic polarization. 2.Primary standard solutions Primary standard KCl solution ,at 25 ℃, 7.419g of KCl in 1000g of solution has a specific conductivity of 0.01286 Ω -1 /cm .

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7 3 . Conductivity Cell : Avoid the change of temperature during determination 4.Wheat stone bridge :

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Factors affecting conductivity: Size of ions Temperature Number of ions Charge of ions Specific conductivity:-It is conductivity offered by a substance of 1cm length and 1sq.cm surface area. units are mhos/cm. Equivalent conductivity:-it is conductivity offered by a solution containing equivalent weight of solute in it. 8

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9 Molar conductance of various ions at infinite dilution at 25℃ ions molar conductance K + 73.52 Na + 50.11 Li + 38.69 H + 349.82 Ag + 61.92 Cl - 76.34 Br - 78.4 OH - 198

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APPLICATIONS OF CONDUCTOMETRY It can be used for the determination of:- Solubility of sparingly soluble salts Ionic product of water Basicity of organic acids Salinity of sea water (oceanographic work) Chemical equilibrium in ionic reactions Conductometric titration 10

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CONDUCTOMETRIC TITRATIONS : The determination of end point of a titration by means of conductivity measurements are known as conductometric titrations. 11

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12 Types of conductometric titrations: Acid-base titration Precipitation titration Replacement titration Redox (oxidation-reduction) titration Complexometric titration

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ACID-BASE TITRATIONS Titration of strong acid (a) with strong base.g. HCl with NaOH (b) with weak base e.g. HCl with NH 4 OH 13

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Titration of weak acid (c) with strong base e.g. CH 3 COOH with NaOH (d) with weak base e.g. CH 3 COOH with NH 4 OH 14

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PRECIPITATION TITRATIONS:- [K + + Cl - ]+[Ag + +No 3 _ ] 15

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REPLACEMENT TITRATIONS Salt of strong acid and weak base vs. strong base Ex: ammonium chloride vs. sodium hydroxide Salt of strong base and weak acid vs. strong acid Eg: sodium acetate vs. hydrochloric acid 16

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a)Salt of strong acid, weak base vs. strong base NH 4 Cl+NaOH →NH 4 OH+NaCl 17

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b)Salt of strong base and weak acid vs. strong acid CH 3 COONa+HCl →CH 3 COOH+NaCl 18

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REDOX TITRATION Titration of ferrous ions with dichromate ions: 6 Fe 2+ +Cr 2 O 7 2- +14H + → 6Fe 3+ +2Cr 3+ +7H 2 O 19

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COMPLEXOMETRIC TITRATION E x.:- KCl vs. Hg(ClO 4 ) 2 N on-aqueous titrations can also be measured using conductometry. Ex:- a)titration of weak bases vs. perchloric acid in dioxan -formic acid. b)Titration of weak organic acids in methanol vs. tetra methyl ammonium hydroxide in methanol-benzene. 20

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ADVANTAGES OF CONDUCTOMETRIC TITRATIONS No need of indicator Colored or dilute solutions or turbid suspensions can be used for titrations. Temperature is maintained constant throughout the titration. End point can be determined accurately and errors are minimized as the end point is being determined graphically. 21

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22 RECENT DEVLOPEMNTS In refinary industries. Estimation of polyelectrolytic solution. Biotechnology. Microbiosensors for enviromental monitoring .

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References Gurdeep.R. chatwal,sham k.anand,instrumental method of chemical analysis,himalaya publishing house,2008,p.no.2.482-2.497. Hovert H.willard,lynne L.merritt,john A.dean,frank A.settle, jr .,instrumental method of analysis CBS publishers 1986,p.no.732-750. Kenneth A. connors,e textbook of pharmaceutical analysis,third edition,wiley india,p.no. 334. Danniel christein,analytical chemistry,2 nd edition,wiley india,p.no. 274. www.pharmapaedia.com 23

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www.authorstream.com Kissinger , P. T., AND W. W. Heineman, eds., Laboratory Techniques in Electroanalytical Chemistry, Dekker, New York, 1984. A.H.beckett ,J.B. stenlake,practical pharmaceutical chemistry,fourth edition ,part –two,p.no-91. Lingane, J.J., Electroanalytical Chemistry, 2 nd ed., Wiley- Interscience , New York, 1958 Continued…. 24

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THANK YOU 25