Question

In the electrochemical series, ions are arranged in an increasing order of discharge potentials.
(A) True
(B) False

Answer 1

Hint: The electrochemical series is the arrangement of various electrode systems in the increasing order of their standard reduction potentials. An electrode with higher standard reduction potential has a high tendency to get reduced, thus the ion will have lower discharge potential.

Complete step by step solution:
Discharge potential is the ability of an ion to get discharged at the electrodes.
The discharge potential of any ion mainly depends on three factors:
(1) The relative position of ions in the electrochemical series.
(2) The relative concentration of ions. The ions with higher concentration will discharge easily.
(3) The nature of the electrodes
Reduction potential is the tendency of the electrodes to accept electrons and as a result it gets reduced.
The cations will get discharged when they gain electrons (or get reduced). The cations with high reduction potential will get discharged easily and will have lower discharge potential. Those which have low reduction potential will have higher discharge potential.
Similarly, anions will get discharged when they lose electrons. Hence anions with higher oxidation potential will have lower discharge potential and those with lower oxidation potential will have lower discharge potential.
Thus discharge potential depends on reduction or oxidation potential.
The cations that have a lower position in the electrochemical series are preferentially discharged and the anions that have a higher position in the electrochemical series are preferentially discharged.
Therefore, in the electrochemical series ions are arranged in an increasing order of discharge potentials.

Hence, option (A) is the correct answer.

Note: At cathode, the reaction involving higher \[{E^0}\] value is preferred i.e., it will be reduced. The increasing order of discharge of few cations at cathode is: ${K^ + },\,C{a^ + },\,N{a^ + },\,M{g^ + },\,A{l^ + },\,Z{n^ + },\,F{e^ + },\,{H^ + },\,C{u^ + },\,A{g^ + }$
At anode, the reaction involving lower \[{E^0}\]value is preferred i.e., it will be oxidised. The increasing order of discharge of few anions at anode is: $SO_4^{2 - },\,NO_3^ - ,\,O{H^ - },\,C{l^ - },\,B{r^ - },\,{H^ - }$
Irrespective of the position of the ions in the electrochemical series there is a tendency to discharge the ions which has a higher concentration.