Oxidation number of Cr atom in `CrO_(5) " and "K_(3)CrO_(8)` respectively

Options

A. `+6, +6`
B. `+5, +6`
C. `+6, +5`
D. `+5, +5`

Answer

To find the oxidation number of chromium (Cr) in the compounds CrO₅ and K₃CrO₈, we will follow these steps:

### Step 1: Determine the oxidation number of Cr in CrO₅

1. **Identify the oxidation state of oxygen**: In most compounds, oxygen has an oxidation state of -2. However, in peroxides and superoxides, it can have different oxidation states. In CrO₅, we need to consider that it contains peroxo groups (O-O bonds).

2. **Set up the equation**: Let the oxidation number of Cr be \( x \). The formula for CrO₅ can be expressed as:
\[ x + 5(-1) = 0 \]
Here, we consider that there are 5 oxygen atoms, and since CrO₅ contains peroxo groups, we treat 4 of the oxygens as -1 and 1 oxygen as -2.

3. **Solve for x**: Rearranging the equation gives:
\[ x - 5 = 0 \implies x = +6 \]
Thus, the oxidation number of Cr in CrO₅ is +6.

### Step 2: Determine the oxidation number of Cr in K₃CrO₈

1. **Identify the oxidation state of oxygen**: In K₃CrO₈, the oxygen typically has an oxidation state of -2. However, we will consider that there are 8 oxygen atoms.

2. **Set up the equation**: Let the oxidation number of Cr be \( x \). The formula for K₃CrO₈ can be expressed as:
\[ 3(+1) + x + 8(-2) = 0 \]
Here, the potassium (K) has an oxidation state of +1.

3. **Solve for x**: Rearranging the equation gives:
\[ 3 + x - 16 = 0 \implies x - 13 = 0 \implies x = +5 \]
Thus, the oxidation number of Cr in K₃CrO₈ is +5.

### Final Answers:
- The oxidation number of Cr in CrO₅ is +6.
- The oxidation number of Cr in K₃CrO₈ is +5.

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