Question

Using the data given, find out in which option the order of reducing power is correct.
\[E_{C{r_2}O_7^{2 - }|C{r^{3 + }}}^\theta \] = 1.33 V
\[E_{C{r_2}|C{l^ - }}^\theta \] = 1.36 V
\[E_{MnO_4^ - |M{n^{2 + }}}^\theta \] = 1.51 V
\[E_{C{r^{3 + }}|Cr}^\theta \] = -0.74V
A. \[C{r^{3 + }}\] < \[C{l^ - }\] < \[M{n^{2 + }}\] < Cr
B. \[M{n^{2 + }}\] < \[C{l^ - }\] < \[C{r^{3 + }}\] < Cr
C. \[C{r^{3 + }}\] < \[C{l^ - }\] < \[C{r_2}O_7^{2 - }\] < \[MnO_4^ - \]
D. \[M{n^{2 + }}\] < \[C{r^{3 + }}\] < \[C{l^ - }\] < Cr

Answer 1

Hint: We can define the reducing character of an atom or a molecule to be the tendency of the given atom or molecule to reduce other chemical species. To put it in simpler terms, in order to reduce other chemical species, the given atom or molecule must itself undergo oxidation. This character is also known as the basic character of a given chemical species. Hence, the reducing character of a given substance is dependent on its basic character

Complete Step-by-Step Answer:
Before we move towards the solution of the given question, let us first understand some important basic concepts.
The electrode potential of hydrogen is considered to be zero as convention everywhere. This gives us a base from where we can find the relative increase or decrease in the reduction potential of the given species.
Electrochemical series is an arrangement of such species in accordance with their reduction potentials with respect to the reduction potential of hydrogen. Now, as we move down in the electrochemical series, the reduction potential decreases. The relation between reduction potential and reducing power is inverse in nature.
In the options given, we can observe the reduction potential in the order:
 \[M{n^{2 + }}\] > \[C{l^ - }\] > \[C{r^{3 + }}\] > Cr
Hence, the reducing power of these species can be given in the order:
 \[M{n^{2 + }}\] < \[C{l^ - }\] < \[C{r^{3 + }}\] < Cr

Hence, Option B is the correct option

Note: Reduction potential can be understood as the measure of the tendency for a given chemical species to accept electrons from other chemical substituents. It is basically the tendency of a species to get reduced by accepting an electron and is quantified on the basis of the electrochemical reference of hydrogen.