exp3 transference number - CHM171L / A11 Physical Chemistry...

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CHM171L / A11 Physical Chemistry Laboratory 2 1 st Quarter S.Y. 2010-2011 Transference Number Calderon, Edna 1 , Palomaria, Ralph Matthew 2 ,Pineda,Jermaine Marianne 2 , Regulacio, Anna Rafaela 2 1 Professor, CHM171L/A11, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology; 2 Student, CHM171L /A11 , School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology ABSTRACT The experiment is on the subject of transference number. The transference number of an ion is the fraction of the total current that is carried by that ion during electrolysis. To determine the transport numbers of hydrogen and nitrate ions, and to relate the transport number with ionic size and mobility are the objectives of this experimentation. From the results, hydrogen ion has higher transference number than nitrate ion. Different ions carry different fractions of the current because different ions move at different speeds under the same potential gradient. It can also be seen that ions are able to move faster when they have a larger ionic mobility and thus, the higher transport number. INTRODUCTION Transference number of an ion is the fraction of the total current that is carried by that ion during electrolysis. Different ions carry different fractions of the current because different ions move at different speeds under the same potential gradient. In general, a cation and an anion differ in the amount of current they can carry during electrolysis. Transport Number (or transference number), is a quantity used in electrochemical calculations. It is the ratio of the current carried by a given ionic species through a cross section of an electrolytic solution to the total current passing through the cross section. The transport number is equal to the ratio of the velocity, or mobility, of a given ion to the sum of the velocities, or mobilities, of the cation and anion. It is a characteristic dependent on the mobilities of all the ions in the electrolytic solution, on the concentrations of the ions, and on the temperature of the solution. The transport number is usually determined by the Hittorf method—that is, by the change in the concentrations of the ions near the electrodes. During electrolysis, ions, owing to solvation, transport not only electric charge but also the solvent in their solvation sheaths. For this reason, transport numbers determined by the Hittorf method are called apparent
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This note was uploaded on 07/31/2011 for the course CHE-CHM-BT CHM171L taught by Professor Calderon during the Spring '11 term at Mapúa Institute of Technology.

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exp3 transference number - CHM171L / A11 Physical Chemistry...

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