Question

Strongest reducing agent is:
(A) $ K $
(B) $ Mg $
(C) $ Al $
(D) $ I $

Answer 1

Hint :We know that the reducing agents are the substance that can donate electrons to reduce the other substance and they get oxidized since they now have lost some of their electrons. The ability of a substance to reduce depends on how easily they can lose their electron and thus in turn depends on the standard electric potential.

Complete Step By Step Answer:
Let us first understand what reducing agents are. In simple words, a reducing agent is an element or compound that “donates” an electron to another compound/element. Since the reducing agent is losing electrons, it is said to have been oxidized. A reducing agent is oxidized because it loses electrons in the redox reaction. Examples of reducing agents are including the earth metals, formic acid and sulfite compounds. A strong reducing agent is nothing but the one that can be easily oxidized by other atoms or molecules. As we know molecules or ions that are easily oxidized usually have average electronegativity and are in a negative oxidation state.
The more the reducing ability of a species the lower its reducing potential should be. So that it can easily get oxidized and reduce the other species. A substance with lower reduction potential tends to donate electrons and hence is said to be a reducing agent. On the other hand, a substance with higher (more positive) reduction potential tends to accept electrons and thus are oxidizing agents. Electrochemical series have metals arranged in order of their standard reduction potential. The oxidation state for Potassium is $ ~+1. $ Hence, Potassium metal is a powerful reducing agent that is easily oxidized to the mono positive cation, $ K+. $ Once oxidized, Potassium is very stable and it is difficult to reduce it.
Therefore, the correct answer is option A.

Note :
Remember that the electrochemical series is also known as the activity series. The series has an arrangement of elements in increasing order of their electrode potential (standard oxidation potential) or decreasing order of standard reduction potential. This has been established by measuring the electrode potential of various elements versus the standard hydrogen electrode. The element at the top of the series is the strong oxidizing agent and the element at the bottom of the series is the strongest reducing agent.