Question:

Given :
\(E^\circ_{\frac{1}{2}\mathrm{Cl_2/Cl^-}} = 1.36\ \mathrm{V},\ E^\circ_{\mathrm{Cr^{3+}/Cr}} = -0.74\ \mathrm{V}\)
\(E^\circ_{\mathrm{Cr_2O_7^{2-}/Cr^{3+}}} = 1.33\ \mathrm{V},\ E^\circ_{\mathrm{MnO_4^-/Mn^{2+}}} = 1.51\ \mathrm{V}\)
The correct order of reducing power of the species \((\mathrm{Cr, Cr^{3+}, Mn^{2+}}\) and \(\mathrm{Cl^-})\) will be :

Show Hint

A species whose oxidised form has a more positive reduction potential is a weaker reducing agent; compare the oxidation potentials of each species.
Updated On: Oct 31, 2026
  • \(\mathrm{Mn^{2+}} \lt \mathrm{Cl^-} \lt \mathrm{Cr^{3+}} \lt \mathrm{Cr}\)
  • \(\mathrm{Mn^{2+}} \lt \mathrm{Cl^{3+}} \lt \mathrm{Cl^-} \lt \mathrm{Cr}\)
  • \(\mathrm{Cr^{3+}} \lt \mathrm{Cl^-} \lt \mathrm{Mn^{2+}} \lt \mathrm{Cr}\)
  • \(\mathrm{Cr^{3+}} \lt \mathrm{Cl^-} \lt \mathrm{Cr} \lt \mathrm{Mn^{2+}}\)
Show Solution
collegedunia
Verified By Collegedunia

The Correct Option is A

Solution and Explanation

Reducing power is measured by the oxidation potential of the species (= -E° of its reverse reduction half-reaction).
\(\mathrm{Cr \rightarrow Cr^{3+}}\): E°(oxidation) = +0.74 V.
\(\mathrm{Cr^{3+} \rightarrow Cr_2O_7^{2-}}\): E°(oxidation) = -1.33 V.
\(\mathrm{Cl^- \rightarrow \frac{1}{2}Cl_2}\): E°(oxidation) = -1.36 V.
\(\mathrm{Mn^{2+} \rightarrow MnO_4^-}\): E°(oxidation) = -1.51 V.
Larger (less negative) oxidation potential means stronger reducing agent: \(\mathrm{Cr} \gt \mathrm{Cr^{3+}} \gt \mathrm{Cl^-} \gt \mathrm{Mn^{2+}}\).
Hence \(\mathrm{Mn^{2+}} \lt \mathrm{Cl^-} \lt \mathrm{Cr^{3+}} \lt \mathrm{Cr}\).
Answer: (1) \(\mathrm{Mn^{2+}} \lt \mathrm{Cl^-} \lt \mathrm{Cr^{3+}} \lt \mathrm{Cr}\)
Was this answer helpful?
0
0