Which of the following given moleculues in a pair are paramagnetic and ferrimagnetic substance respectively?

Options

A. `Fe_3 O_4` & `H_2 O`
B. `MnO` & `CrO_2`
C. `Cu^(2+)` & `ZnFe_2 O_4`
D. `C_6 H_6' & 'O_2`

Answer

To determine which of the given molecules in a pair are paramagnetic and ferrimagnetic substances, we need to analyze the properties of each substance based on their electronic configurations and magnetic behavior.

### Step-by-Step Solution:

1. **Understanding Paramagnetic Substances:**
- Paramagnetic substances are those that have unpaired electrons in their atomic or molecular orbitals. These unpaired electrons cause the substance to be attracted to a magnetic field.
- Example: Oxygen (O2) is paramagnetic because it has unpaired electrons.

2. **Understanding Ferrimagnetic Substances:**
- Ferrimagnetic substances have unequal opposing magnetic moments due to the arrangement of their magnetic domains. They exhibit a net magnetic moment, but it is less than what would be expected based on the number of unpaired electrons.
- Example: Magnetite (Fe3O4) is a classic example of a ferrimagnetic material.

3. **Analyzing the Options:**
- **Option 1: Fe3O4 and H2O**
- Fe3O4 (magnetite) is ferrimagnetic due to its structure and the presence of unpaired electrons.
- H2O (water) is diamagnetic because it has all paired electrons.
- **Option 2: MnO and CrO2**
- MnO is antiferromagnetic, which does not fit our criteria.
- CrO2 is known to be ferromagnetic, but we are looking for ferrimagnetic substances.
- **Option 3: Cu^2+ and ZnFe2O4**
- Cu^2+ has a d9 configuration, meaning it has one unpaired electron, making it paramagnetic.
- ZnFe2O4 is ferrimagnetic because it contains both Zn^2+ and Fe^3+ ions, leading to unequal opposing magnetic moments.
- **Option 4: C6H6 (Benzene)**
- Benzene is diamagnetic due to its fully filled π orbitals.

4. **Conclusion:**
- From the analysis, the pair that contains a paramagnetic substance and a ferrimagnetic substance is **Option 3: Cu^2+ (paramagnetic) and ZnFe2O4 (ferrimagnetic)**.

### Final Answer:
**Option 3: Cu^2+ and ZnFe2O4**