Assertion :- Oxidation number of `Cr` in `CrO_(3)` is `+6`.
Reason :- In `CrO_(5)`, four oxygen atoms are involved in peroxide linkage.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False.

Answer

To solve the given question, we need to analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states that the oxidation number of chromium (Cr) in chromium trioxide (CrO3) is +6.

To find the oxidation number of Cr in CrO3:
- Let the oxidation number of Cr be \( x \).
- Each oxygen atom has an oxidation number of -2. Since there are 3 oxygen atoms, the total contribution from oxygen is \( 3 \times (-2) = -6 \).
- The compound is neutral, so the sum of oxidation numbers must equal 0.

Setting up the equation:
\[ x + (-6) = 0 \]
\[ x - 6 = 0 \]
\[ x = +6 \]

Thus, the oxidation number of Cr in CrO3 is indeed +6. Therefore, the assertion is **true**.

### Step 2: Analyze the Reason
The reason states that in CrO5, four oxygen atoms are involved in a peroxide linkage.

To understand this, we need to look at the structure of CrO5:
- CrO5 consists of one chromium atom and five oxygen atoms.
- In CrO5, typically, there are two types of oxygen bonding: one double bond with one oxygen and four oxygen atoms that are involved in peroxide linkages.

Peroxide linkage refers to the bond between two oxygen atoms (O-O) where each of these oxygen atoms is also bonded to another element (in this case, chromium).

Thus, the reason provided is also **true**.

### Step 3: Determine the Relationship Between Assertion and Reason
While both the assertion and reason are true, the reason does not explain why the oxidation number of Cr in CrO3 is +6. The reason pertains to a different compound (CrO5) and its structure rather than explaining the oxidation state in CrO3.

### Conclusion
- The assertion is true: the oxidation number of Cr in CrO3 is +6.
- The reason is true: in CrO5, four oxygen atoms are involved in peroxide linkage, but it does not explain the assertion.

Thus, the correct answer is:
**Both assertion and reason are true, but reason is not the correct explanation for the assertion.**

### Final Answer
**Option B**: Both assertion and reason are true, but reason is not the correct explanation for the assertion.

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