Transport number

education

1. PRESENTED BY Khondaker Afrina Hoque Roll: 1114015 R eg: 900048 Session : 2011-12 1 8/18/2015

2. PRESENTATION ON TRANSFORT NUMBER AND FECTORS AFFECTING TRANSFORT NUMBERS 2 8/18/2015

3. 3 8/18/2015 TRANSFORT NUMBER OR TRANSFERENCE NUMBER WHAT IS TRANSPORT NUMBER ? “The fraction of the current carried by a given ionic species in the solution is called the transport number of Hittorf’s number or transference number of the ion ” . If v+ represents the speed of migration of the cation and v– that of the anion, the transport number of cation = v+ v - + v + the transport number of anion = v- v - + v + And t + +t - =1

4. MECHANISM OF IONIC TRANSPORT The following cases may now be considered : ( i ) Let the anions alone be capable of movement. ( ii) Let the anions and cations move at the same ( iii) Let the cations move at twice the speed of the anions 4 8/18/2015 FIGURE : Mechanism of ionic transport .

5. METHODS OF DETERMINATION OF TRANSFORT NUMBER Hittorf,s Method. Moving boundary method . Abnormal transport numbers 5 8/18/2015 Exhibits a marked deviation in transport number with concentration. Example:Cadmium iodide. Explanation: In conc. Solution- CdI 2 + 2I CdI 4 2 -

6. FACTORS AFFECTING TRANSFORT NUMBERS 1 . Variation of transport number with concentration The variation of the transport numbers with the concentration of the electrolyte was proposed by onsager,i,e ., t=t -A √C 6 8/18/2015 For 1,1-electrolytes . 1.Cause of conc. Dependence: 2.The results lead to generalization that- When t + is close to 0.5 When t + <0.5. when t + >0.5.

7. For 2,1-electrolytes . 1.Effect: 2.Cause: 3.example: For 2,2-electrolytes. 1.Effect: 2.cause: 3:Example: 7 8/18/2015

8. 2.Variation of transport number with temperature Effects: t + increases with the increase of temperature. t - decreases with the increase of temperature. Transport number greater than 0.5 decreases with the increase in temperature. Transport number less than 0.5 increases with rise in temperature. 8 8/18/2015

9. 3 .Variation of transport number with electrolyte. ELECTROLYTE t + ELECTROLYTE t - KCl 0.490 HCl 0.177 KBr 0.488 LiCl 0.662 KNO 3 0.508 NaCl 0.605 KCl 0.510 9 8/18/2015

10. Thank’s to all….. 10 8/18/2015