In chromite ore, the oxidation number of iron and chromium are respectively.

Options

A. `+3, +2`
B. `+3, +6`
C. `+2, +6`
D. `+2,+3`

Answer

To determine the oxidation numbers of iron and chromium in chromite ore (FeCr2O4), we can follow these steps:

### Step 1: Identify the formula of chromite ore
The formula for chromite ore is FeCr2O4.

### Step 2: Assign oxidation states to the components
In the formula FeCr2O4, we have:
- Iron (Fe)
- Chromium (Cr)
- Oxygen (O)

### Step 3: Determine the oxidation state of oxygen
Oxygen typically has an oxidation state of -2.

### Step 4: Calculate the total contribution of oxygen
In FeCr2O4, there are 4 oxygen atoms:
Total contribution from oxygen = 4 × (-2) = -8.

### Step 5: Set up the oxidation state equation
Let the oxidation state of iron be x and that of chromium be y. The formula can be represented as:
x + 2y + (-8) = 0.

### Step 6: Solve for the oxidation states
From the formula, we can set up the equation:
x + 2y - 8 = 0.

### Step 7: Use known oxidation states
We know that in chromite ore, iron typically has an oxidation state of +2 and chromium has an oxidation state of +3. We can verify this:
- If Fe = +2, then x = +2.
- If Cr = +3, then y = +3.

### Step 8: Substitute the values into the equation
Substituting these values into the equation:
2 + 2(3) - 8 = 0,
2 + 6 - 8 = 0,
0 = 0, which confirms our oxidation states.

### Conclusion
Thus, the oxidation numbers of iron and chromium in chromite ore (FeCr2O4) are:
- Iron (Fe): +2
- Chromium (Cr): +3

### Final Answer
The oxidation numbers of iron and chromium in chromite ore are +2 and +3, respectively.

---