Question

State True or False.
The sum of two transport numbers of an electrolyte is equal to one.
A. True
B. False

Answer 1

Hint: The concept of transport number was introduced by Johann Wilhelm Hittorf in 1853. Liquid junction potential arises from ions in a solution which have different ion transport numbers.

Complete answer:
- Ion transport number or transference number is the fraction of the total electric current carried in an electrolyte by ionic species.
- Differences in transport number arise from differences in their electrical mobility. Like in a solution of sodium chloride more than half is carried by the anions or chloride ions and less than half of the current is carried by the cations or sodium ions because chloride ions move faster that is chloride ions have higher mobility than sodium ions. The sum of the transport numbers of all the ions in a solution always equals one or unity.
- Hittorf method measures ion concentration changes near the electrodes and the moving boundary method measures the speed of displacement of boundary between two solutions due to an electric current.
- Rise in temperature affects transport number. With a rise in temperature, the transference number of cation and anion comes closer to half.
The answer is that the given statement is true which is option ‘a’ that the sum of two transport numbers of an electrolyte is equal to one.

Note: There is a difference between transport number and oxidation number. The terms are completely different. Transport number seems to be the electrons that are transferred in the reaction. But this is not true. Transference number is the amount of fractional current.