Which of the following statements is/are false ?

Options

A. `MgO` has greater lattice energy than `NaCl` .
B. `KHF_(2)` exist but `KHCl_(2)` do not .
C. `Fe^(2+)` Is more stable than `Fe^(3+)`
D. In Vinyl Chloride the C---Cl bond length is shorter than expected

Explanation

To determine which of the statements is false, we will evaluate each statement one by one.

### Statement 1: MgO has greater lattice energy than NaCl.

**Analysis:**
- Lattice energy depends on the charges of the ions and the distance between them.
- MgO consists of Mg²⁺ and O²⁻ ions, while NaCl consists of Na⁺ and Cl⁻ ions.
- The charges on Mg²⁺ and O²⁻ are both +2 and -2, respectively, which are higher than the +1 and -1 charges of Na⁺ and Cl⁻.
- Therefore, MgO has greater lattice energy than NaCl.

**Conclusion:** This statement is **true**.

### Statement 2: KHf2 exists but KHCl2 does not.

**Analysis:**
- HF can form hydrogen bonds due to the high electronegativity of fluorine, leading to the formation of the HF₂⁻ ion.
- This ion can combine with K⁺ to form KHf₂.
- In contrast, HCl does not form a similar ion (HCl₂⁻) because it does not exhibit hydrogen bonding.
- Hence, KHCl₂ cannot exist.

**Conclusion:** This statement is **true**.

### Statement 3: Fe²⁺ is more stable than Fe³⁺.

**Analysis:**
- The electronic configuration of Fe is [Ar] 3d⁶ 4s².
- For Fe²⁺, the configuration is [Ar] 3d⁶.
- For Fe³⁺, the configuration is [Ar] 3d⁵ (removing two electrons from the 4s and one from the 3d).
- The 3d⁵ configuration in Fe³⁺ is half-filled, which is more stable due to maximum spin multiplicity.
- Therefore, Fe³⁺ is more stable than Fe²⁺.

**Conclusion:** This statement is **false**.

### Statement 4: In vinyl chloride, the Cl bond length is shorter than expected.

**Analysis:**
- Vinyl chloride (C₂H₃Cl) has a structure where the chlorine atom can participate in resonance with the double bond.
- The presence of resonance leads to partial double bond character in the C-Cl bond.
- This partial double bond character results in a shorter bond length than what would be expected for a single bond.

**Conclusion:** This statement is **true**.

### Final Conclusion:
The false statement is **Statement 3: Fe²⁺ is more stable than Fe³⁺**.

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