Oxidation state of the metal in the minerals haematite and magnetite, respectively are

Options

A. II, III in haematite and III in magnetite
B. II, III in haematite and II in magnetite
C. II in haematite and ll, III in magnetite
D. III in haematite and ll, III in magnetite

Answer

To determine the oxidation states of the metal in the minerals haematite and magnetite, we will analyze the chemical formulas of these minerals and the oxidation states of iron (Fe) in each.

### Step-by-Step Solution:

1. **Identify the Chemical Formulas:**
- Haematite is represented by the formula \( \text{Fe}_2\text{O}_3 \).
- Magnetite is represented by the formula \( \text{Fe}_3\text{O}_4 \).

2. **Determine the Oxidation State in Haematite:**
- In haematite (\( \text{Fe}_2\text{O}_3 \)), oxygen typically has an oxidation state of -2.
- Since there are three oxygen atoms, the total oxidation contribution from oxygen is \( 3 \times (-2) = -6 \).
- Let the oxidation state of iron (Fe) be \( x \). The equation for the total oxidation state is:
\[ 2x + (-6) = 0 \]
- Solving for \( x \):
\[ 2x = 6 \implies x = 3 \]
- Therefore, the oxidation state of iron in haematite is +3.

3. **Determine the Oxidation State in Magnetite:**
- In magnetite (\( \text{Fe}_3\text{O}_4 \)), we can consider it as a combination of \( \text{FeO} \) and \( \text{Fe}_2\text{O}_3 \).
- Here, there are four oxygen atoms contributing a total oxidation state of \( 4 \times (-2) = -8 \).
- Let the oxidation states of the three iron atoms be \( x_1, x_2, x_3 \). The equation is:
\[ x_1 + x_2 + x_3 + (-8) = 0 \]
- In magnetite, two of the iron atoms are in the +2 oxidation state and one is in the +3 oxidation state. Thus:
\[ 2(+2) + 1(+3) = +4 + +3 = +7 \]
- The total oxidation state from iron must balance the -8 from oxygen, hence:
\[ +7 - 8 = -1 \text{ (which is balanced)} \]
- Therefore, in magnetite, the oxidation states of iron are +2 and +3.

4. **Conclusion:**
- The oxidation state of iron in haematite is +3.
- The oxidation states of iron in magnetite are +2 and +3.

### Final Answer:
The oxidation states of the metal in haematite and magnetite are +3 and +2/+3, respectively.