Which is not the property of diamond?

Options

A. It is insoluble in all solvents
B. it is oxidised with a mixture of `K_(2)Cr_(2)O_(7)` and `H_(2)SO_(4)` at `200^(@)C`
C. Being hardest, it is used as an abrasive for sharpening hard tools.
D. `Delta_(f)H^(o.)` value of diamound is `1.90 kJ mol^(-1)`

Explanation

To determine which option is not a property of diamond, we will analyze each option step by step.

### Step 1: Analyze Option 1 - Insoluble in all solvents
- Diamond is a covalent network solid, meaning it has a strong covalent bond throughout its structure.
- Due to this strong bonding, diamond is indeed insoluble in most solvents.
- **Conclusion**: This statement is true.

### Step 2: Analyze Option 2 - Oxidized with the mixture of dichromate and sulfuric acid
- Diamond is known for its stability and hardness.
- It is resistant to oxidation, even with strong oxidizing agents like acidified dichromate.
- **Conclusion**: This statement is false because diamond cannot be oxidized by this mixture.

### Step 3: Analyze Option 3 - Used as an abrasive for sharpening the hardest tools
- Due to its extreme hardness, diamond is commonly used as an abrasive material.
- It is effective in cutting and sharpening tools.
- **Conclusion**: This statement is true.

### Step 4: Analyze Option 4 - Delta H of fusion of diamond is 1.90 kJ/mol
- The enthalpy of fusion (ΔH_fusion) for diamond is indeed around 1.90 kJ/mol.
- This is a recognized thermodynamic property of diamond.
- **Conclusion**: This statement is true.

### Final Conclusion:
After analyzing all the options, we find that the statement which is **not a property of diamond** is **Option 2**, which claims that diamond can be oxidized with a mixture of dichromate and sulfuric acid.

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