Question

The correct order of following 3d metal oxides, according to their oxidation numbers is :
(a) $CrO_3$
(b) $Fe_2O_3$
(c) $MnO_2$
(d) $V_2O_5$
(e) $Cu_2O$

• (a) > (c) > (d) > (b) > (e)
• (a) > (d) > (c) > (b) > (e)
• (d) > (a) > (b) > (c) > (e)
• (c) > (a) > (d) > (e) > (b)

Hint:

Oxidation states in transition metal oxides usually correspond to the maximum valency for higher oxidation states (like Cr and V).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The oxidation number of a metal in an oxide is calculated based on the fact that Oxygen typically has an oxidation state of \(-2\).
Step 2: Key Formula or Approach:
Sum of oxidation states in a neutral molecule = 0.
Step 3: Detailed Explanation:
Calculate the oxidation state of the metal in each oxide:
- (a) \(CrO_3\): \(x + 3(-2) = 0 \implies x = +6\).
- (b) \(Fe_2O_3\): \(2x + 3(-2) = 0 \implies 2x = 6 \implies x = +3\).
- (c) \(MnO_2\): \(x + 2(-2) = 0 \implies x = +4\).
- (d) \(V_2O_5\): \(2x + 5(-2) = 0 \implies 2x = 10 \implies x = +5\).
- (e) \(Cu_2O\): \(2x + 1(-2) = 0 \implies 2x = 2 \implies x = +1\).
The order is: \(+6 (a)>+5 (d)>+4 (c)>+3 (b)>+1 (e)\).
Step 4: Final Answer:
The correct order is (B).