The number of pages within the document is: 4
The self-declared author(s) is/are:
Administrator
The subject is as follows:
Original authors did not specify.
The original URL is: LINK
The access date was:
2019-02-10 17:22:05.207071
Please be aware that this may be under copyright restrictions. Please send an email to admin@pharmacoengineering.com for any AI-generated issues.
Loading...
Reload document 
Open in new tab The content is as follows:
68 Electroanalytical Methods-II 6.2.4 Conductometric Titrations The principle of conductometric titration is based on the fact that during the titration, one of the ions is replaced by the other and invari ably these two ions differ in the ionic conductivity with the result that conductivity of t he solution varies during the course of titration. The equivalence point may be located graphically by plotting the change in conductance as a function of the volume of titra nt added. In order to reduce the influence of errors in the c onductometric titration to a minimum, the angle between the two branches of the titration curve should be as small as possible (see Fig. 6.2). If the angle is very obtus e, a small error in the conductance data can cause a large deviation. The following app roximate rules will be found useful. · The smaller the conductivity of the ion which repla ces the reacting ion, the more accurate will be the result. Thus it is preferable to titrate a silver salt with lithium chloride rather than with HCl. Generally, cations should be titrated with lithium salts and anions with acetates as these ion s have low conductivity (Table 4.2 of Unit 4). · The larger the conductivity of the anion of the rea gent which reacts with the cation to be determined, or vice versa, the more ac ute is the angle of titration curve. · The titration of a slightly ionized salt does not g ive good results, since the conductivity increases continuously from the commen cement. Hence, the salt present in the cell should be virtually completely dissociated; for a similar reason; the added reagent should also be as strong electrolyte. · Throughout a titration the volume of the solution i s always increasing, unless the conductance is corrected for this effect, non linea r titration curves result. The correction can be accomplished by multiplying the o bserved conductance either by total volume ( V+V´) or by the factor ( V+ V´)/ V, where V is the initial volume of solution and V´ is the total volume of the reagent added. The cor rection presupposes that the conductivity is a linear funct ion of dilution, this is true only to a first approximation. · In the interest of keeping V small, the reagent for the conductometric titratio n is ordinarily several times more concentrated than the solution being titrated (at least 10-20 times). A micro burette may then be use d for the volumetric measurement. The main advantages to the conductometric titration are its applicability to very dilute, and coloured solutions and to system that involve r elative incomplete reactions. For example, which neither a potentiometric, nor indica tor method can be used for the neutralization titration of phenol ( Ka = 10 Œ10 ) a conductometric endpoint can be successfully applied. Application: Acid-base titration, especially at tra ce levels. Relative precision better than 1% at all levels. There are also few disadvant ages with this technique. As you know the conductance is a non-specific property, co ncentration of other electrolyte can be troublesome. The electrical conductance of a solution is a measu re of its currents carrying capacity and therefore determined by the total ionic strengt h. It is a non-specific property and for this reason direct conductance measurement are of little use unless the solution contains only the electrolyte to be determined or t he concentrations of other ionic species in the solution are known. Conductometric t itrations, in which the species in the solution are converted to non-ionic for by neut ralization, precipitation, etc. are of more value.
Please note all content on this page was automatically generated via our AI-based algorithm (80EJuhrsxs5WggHkkTMs). Please let us know if you find any errors.