JEE Main 2021 — D And F Block Elements Question with Solution
From: JEE Main 2021 (Online) 25th July Morning Shift
Question
The correct order of following 3d metal oxides, according to their oxidation numbers is :
(a) CrO3, (b) Fe2O3, (c) MnO2, (d) V2O5, (e) Cu2O
(a) CrO3, (b) Fe2O3, (c) MnO2, (d) V2O5, (e) Cu2O
Choose an option
Show full solutionCorrect option: C
Correct answer
C(a) > (d) > (c) > (b) > (e)
Step-by-step explanation
(a) : Since there are three oxygen atoms each with an oxidation number of -2, the total oxidation number from the oxygen atoms is -6. To make the compound neutral, Chromium (Cr) must therefore have an oxidation number of +6.
(b) : Here, there are three oxygen atoms, contributing a total oxidation number of -6. To balance this, the total oxidation number for the two iron (Fe) atoms must be +6, meaning each Fe atom has an oxidation number of +3.
(c) : With two oxygen atoms, the total oxidation number is -4. Thus, the manganese (Mn) atom must have an oxidation number of +4 to balance this.
(d) : In this case, there are five oxygen atoms for a total oxidation number of -10. To balance this, the total oxidation number for the two vanadium (V) atoms must be +10, meaning each V atom has an oxidation number of +5.
(e) : Here, there's one oxygen atom with an oxidation number of -2. To balance this, the total oxidation number for the two copper (Cu) atoms must be +2, meaning each Cu atom has an oxidation number of +1.
So, the order of the oxidation numbers from highest to lowest is :
(a) CrO > (d) VO > (c) MnO > (b) FeO > (e) CuO.
Therefore, the answer is Option C : (a) > (d) > (c) > (b) > (e).
(b) : Here, there are three oxygen atoms, contributing a total oxidation number of -6. To balance this, the total oxidation number for the two iron (Fe) atoms must be +6, meaning each Fe atom has an oxidation number of +3.
(c) : With two oxygen atoms, the total oxidation number is -4. Thus, the manganese (Mn) atom must have an oxidation number of +4 to balance this.
(d) : In this case, there are five oxygen atoms for a total oxidation number of -10. To balance this, the total oxidation number for the two vanadium (V) atoms must be +10, meaning each V atom has an oxidation number of +5.
(e) : Here, there's one oxygen atom with an oxidation number of -2. To balance this, the total oxidation number for the two copper (Cu) atoms must be +2, meaning each Cu atom has an oxidation number of +1.
So, the order of the oxidation numbers from highest to lowest is :
(a) CrO > (d) VO > (c) MnO > (b) FeO > (e) CuO.
Therefore, the answer is Option C : (a) > (d) > (c) > (b) > (e).
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