Question

Equivalent weight of $MnO_4^ -$ is equal to molecular weight, when it changes into new species X.
What is X? It is by oxidation or reduction.
(A) Reduction
(B) Oxidation
(C) Neither oxidation nor reduction
(D) None of these

Answer 1

Hint - To solve this problem we should know about oxidation, reduction, oxidation state and all the knowledge regarding them and hence, by using this information we can easily approach the answer.

Complete step by step solution:

Oxidation: It is chemical change which involves the loss of electrons during a reaction by a molecule, atom or ion. Oxidation appears when the oxidation state of a molecule, atom or ion is increased.
Reduction: reduction is defined as chemical change that involves the gaining of electrons by one of the atoms associated in the reaction between two chemicals. The term suggests itself that the element accepts electrons, as the oxidation state of the element that gains electrons is lowered.
Oxidation state: Oxidation state illustrates the degree of oxidation of an atom in a chemical compound. The sum of the oxidation numbers of all of the atoms in a molecule or ion must be = in sign and value to the charge on the molecule or ion.
The highest oxidation state of $Mn$ is$+ 7$ in $MnO_4^ -$ .Hence the oxidation state decreases by one unit to $+ 6$ .
$MnO_4^{ - 1} \to MnO_4^{2 - }$
The above reaction shows Reduction.

So, the correct answer is option A – Reduction.

Note - The oxidation state of an element correlates to the number of electrons that an atom loses, gains, or appears to use when joining with other atoms in the compound. The overall oxidation state of all atoms in a neutral atom or molecule is 0 and in an ion is equal to the ion charge. Group 1 metals have an oxidation state of $+ 1$ and group 2 an oxidation state of $+ 2$ . Oxidation state of fluorine is -1 in compounds. Oxygen generally has an Oxidation state of $- 2$ in compounds