Question

Arrange the following in the order of their decreasing electrode potential: Mg, K, Li, Ca.
A. K, Li, Ca, Mg
B. Li, Ca, K, Mg
C. Ca, Mg, K, Li
D. Mg, Ca, K, Li

Answer 1

Hint: Electrode potential refers to the potential difference that develops during a cell reaction between electrode and the electrolyte, potential observed at the oxidation half is known as oxidation potential, and the potential observed at the reduction half is known as reduction potential

Complete Answer:
The electrode potential is often measured using a standard hydrogen electrode as the reference electrode. Decreasing order of electrode potential of the following given element can be written using the standard electrode potential at 298K table.
And according to the table, in the given sets of the elements, the highest negative value of standard electrode potential is possessed by Li, followed by K, Ca, and the least negative value of standard electrode potential is possessed by Mg.

Therefore we can write the decreasing order of electrode potential element as;
${\text{Mg }}\rangle {\text{ Ca }}\rangle {\text{ K }}\rangle {\text{ Li}}$

Hence, the correct answer is option (D) i.e. Mg, Ca, K, Li.

Additional information:
Standard electrode potential - When the concentration of all the species is taken as unity in the half cell reaction, then the calculated electrode potential is called the standard electrode potential.

Note: Remember that all the values of the electrode potentials are given in negative sign, hence the highest negative value means the lowest electrode potential, because of the mathematical fact that -1 is the greatest value in the negative integer.