conductometry


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  Notes
 
 
1 : CONDUCTOMETRY
2 : 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(?-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 ??=1/??
3 : From this unknown resistance was calculated, the reciprocal of this resistance gives conductivity.
4 : Factors affecting conductivity: 1)Number of ions 2)Charge of ions 3)Size of ions 4)Temperature 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.
5 : APPLICATIONS OF CONDUCTOMETRY It can be used for the determination of:- 1)Solubility of sparingly soluble salts 2)Ionic product of water 3)Basicity of organic acids 4)Purity of water 5)Salinity of sea water 6)Chemical equilibrium in ionic reactions
6 : CONDUCTOMETRIC TITRATIONS: The determination of end point of a titration by means of conductivity measurements are known as conductometric titrations. Types of conductometric titrations: Acid-base titration Precipitation titration Replacement titration Redox (oxidation-reduction) titration Complexometric titration
7 : ACID-BASE TITRATIONS . Titration of strong acid (a) with strong base.g. HCl with NaOH (b) with weak base e.g. HCl with NH4OH
8 : . Titration of weak acid (c) with strong base e.g. CH3COOH with NaOH (d) with weak base e.g. CH3COOH with NH4OH
9 : PRECIPITATION TITRATIONS:- a)Only one product is a precipitate b)When precipitates are sparingly soluble
10 : REPLACEMENT TITRATIONS a)Salt of strong acid and weak base vs strong base Eg: ammonium chloride vs sodium hydroxide b)Salt of strong base and weak acid vs strong acid Eg: sodiumacetate vs hydrochloric acid
11 : a)Salt of strong acid, weak base vs strong base NH4Cl+NaOH?NH4OH+NaCl
12 : b)Salt of strong base and weak acid vs strong acid CH3COONa+HCl?CH3COOH+NaCl
13 : REDOX TITRATION Titration of ferrous ions with dichromate ions: 6 Fe2++Cr2O72-+14H+?6Fe3++2Cr3++7H2O
14 : COMPLEXOMETRIC TITRATION e.g.:-KCl vs Hg(ClO4)2 Non-aqueous titrations can also be measured using conductometry. e.g:- a)titration of weak bases vs perchloric acid in dioxan-formic acid. b)Titration of weak organic acids in methanol vs tetramethyl ammonium hydroxide in methanol-benzene.
15 : ADVANTAGES OF CONDUCTOMETRIC TITRATIONS No need of indicator Coloured 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 minimised as the end point is being determined graphically.
16 : THANK YOU -P.V.R.G.RANGACHARYULU

 

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