Question

Selective discharge of ions depends on:
A. the nature of the electrode
B. the relative concentration of ions
C. the relative position of ions in the electrochemical (activity) series
D. all of the above

Answer 1

Hint: To answer this question we should know what is selective discharge and factors affecting it. In electrolysis, current is passed in the molten state of the ionic compound. The compound decomposes into ions. The anion loses electrons at anode and gets discharged and cation gets electrons at cathode and gets discharged. If two or more same changed ions are present then there will be competition for discharge which is known as selective discharge

Complete step by step answer:In selective discharge only one type of ion gets discharged at an electrode. The discharge of the ion depends upon the following factors:

1) Nature of the electrode: When molten sodium chloride is electrolysed using mercury electrode. There is competition between hydrogen ions and sodium ions. The sodium ion gets discharged selectively even though the reduction potential of sodium is lower than hydrogen.

2) The relative concentration of ions:The ions which are present in high concentration get deposited first.

3) The relative position of ions in the electrochemical (activity) series:

In case of cation, the species having high reduction potential get discharged first. In case of anion, the species having low reduction potential get discharged first.

So, selective discharge of ions depends on the nature of the electrode, the relative concentration of ions and the relative position of ions in the electrochemical (activity) series.

Therefore, option (D) all of the above, is correct.

Note:Electrolysis is a process used for the separation of metal and non-metals. In electrolysis, the ionic compound is taken into the electrolytic cell. The cell also has two electrodes, positively charged anode and negatively charged cathode. The electrochemical series is a series of elements, in which elements are arranged according to their reduction potential. The reduction potential of an element tells the ease of reduction of an element. The cation gets electrons to get discharged, so the cation having high reduction potential will get electrons first and get discarded. Similarly, anion having low reduction potential loses electrons easily and gets discharged.