Question

In acidic medium, H₂O₂ changes Cr₂O₇^2- to CrO₅ which has two (-O-O-) bonds. Oxidation state of Cr in CrO₅ is

• A. +3
• B. +6
• C. -10
• D. +5

Answer 1

The Correct Option is B

The question requires determining the oxidation state of Chromium (Cr) in the compound CrO₅. Let's break down the problem step-by-step to find the answer:

1. First, understand the composition of CrO₅:
   • The compound CrO₅ consists of one Chromium (Cr) atom and five Oxygen (O) atoms.
2. It is known that CrO₅ has a structure with two (-O-O-) peroxy bonds. Each peroxy bond involves two oxygen atoms sharing two electrons, which makes the bond oxidation number unusual compared to normal singly bonded oxygen.
3. The oxidation state of each oxygen in a normal O^2- bond is -2. However, in a peroxide (O-O) bond, like in hydrogen peroxide (H₂O₂), the oxidation state for each oxygen is -1.
4. Given that CrO₅ contains two peroxide bonds, it involves four O atoms each with an oxidation state of -1, and one normal O atom with an oxidation state of -2. Therefore, the total oxidation contributions from the oxygens are: 4 \times (-1) + 1 \times (-2) = -4 - 2 = -6.
5. To find the oxidation state of Cr, let it be x. The sum of oxidation states in a neutral complex must equal zero. Therefore, we set up the equation: x + (-6) = 0.
6. Solving for x, we find: x = +6.

Therefore, the oxidation state of Chromium in CrO₅ is +6.

Correct Answer: +6