Find out number of transformation among following which involves the change of hybridisation of underlined atom.
(a) `H_(2)underline(O)+H^(+) to H_(3)underline(O)^(+) " " (b) NH_(3)+underline(B)F_(3) to NH_(3). Underline(B)F_(3)`
(c ) `underline(X)eF_(6) to underline(X)eF_(5)^(+)+F^(-) " " (d) 2underline(P) Cl_(5) to underline(P)Cl_(4)^+)+PCl_(6)^(-)`
(e ) ` underline(C )H_(3)-CH_(3) to underline(C )H_(3)^(-)+CH_(3)^(+)`

Explanation

To determine the number of transformations that involve a change of hybridization of the underlined atoms in the given reactions, we will analyze each transformation step by step.

### Step 1: Analyze the first transformation
**Transformation (a)**: \( H_2\underline{O} + H^+ \rightarrow H_3\underline{O}^+ \)

- **Hybridization of Oxygen in \( H_2O \)**:
- Oxygen has 2 bond pairs (H-O bonds) and 2 lone pairs.
- Steric number = 2 (bond pairs) + 2 (lone pairs) = 4.
- Hybridization = \( sp^3 \).

- **Hybridization of Oxygen in \( H_3O^+ \)**:
- Oxygen has 3 bond pairs (H-O bonds) and 1 lone pair.
- Steric number = 3 (bond pairs) + 1 (lone pair) = 4.
- Hybridization = \( sp^3 \).

**Conclusion**: No change in hybridization.

### Step 2: Analyze the second transformation
**Transformation (b)**: \( NH_3 + \underline{BF_3} \rightarrow NH_3.\underline{BF_3} \)

- **Hybridization of Boron in \( BF_3 \)**:
- Boron has 3 bond pairs (B-F bonds) and 0 lone pairs.
- Steric number = 3 (bond pairs) + 0 (lone pairs) = 3.
- Hybridization = \( sp^2 \).

- **Hybridization of Boron in \( NH_3.BF_3 \)**:
- Boron now has 4 bonds (3 B-F bonds and 1 coordinate bond with NH3).
- Steric number = 4 (bond pairs) + 0 (lone pairs) = 4.
- Hybridization = \( sp^3 \).

**Conclusion**: Change in hybridization from \( sp^2 \) to \( sp^3 \).

### Step 3: Analyze the third transformation
**Transformation (c)**: \( \underline{XeF_6} \rightarrow \underline{XeF_5}^+ + F^- \)

- **Hybridization of Xenon in \( XeF_6 \)**:
- Xenon has 6 bond pairs (Xe-F bonds) and 0 lone pairs.
- Steric number = 6 (bond pairs) + 0 (lone pairs) = 6.
- Hybridization = \( sp^3d^2 \).

- **Hybridization of Xenon in \( XeF_5^+ \)**:
- Xenon has 5 bond pairs (Xe-F bonds) and 1 lone pair.
- Steric number = 5 (bond pairs) + 1 (lone pair) = 6.
- Hybridization = \( sp^3d^2 \).

**Conclusion**: No change in hybridization.

### Step 4: Analyze the fourth transformation
**Transformation (d)**: \( 2\underline{PCl_5} \rightarrow \underline{PCl_4}^+ + PCl_6^- \)

- **Hybridization of Phosphorus in \( PCl_5 \)**:
- Phosphorus has 5 bond pairs (P-Cl bonds) and 0 lone pairs.
- Steric number = 5 (bond pairs) + 0 (lone pairs) = 5.
- Hybridization = \( sp^3d \).

- **Hybridization of Phosphorus in \( PCl_4^+ \)**:
- Phosphorus has 4 bond pairs (P-Cl bonds) and 0 lone pairs.
- Steric number = 4 (bond pairs) + 0 (lone pairs) = 4.
- Hybridization = \( sp^3 \).

**Conclusion**: Change in hybridization from \( sp^3d \) to \( sp^3 \).

### Step 5: Analyze the fifth transformation
**Transformation (e)**: \( \underline{C}H_3-CH_3 \rightarrow \underline{C}H_3^- + CH_3^+ \)

- **Hybridization of Carbon in \( C_2H_6 \)**:
- Each carbon has 4 bond pairs (C-H bonds) and 0 lone pairs.
- Steric number = 4 (bond pairs) + 0 (lone pairs) = 4.
- Hybridization = \( sp^3 \).

- **Hybridization of Carbon in \( CH_3^- \)**:
- Carbon has 3 bond pairs (C-H bonds) and 1 lone pair.
- Steric number = 3 (bond pairs) + 1 (lone pair) = 4.
- Hybridization = \( sp^3 \).

- **Hybridization of Carbon in \( CH_3^+ \)**:
- Carbon has 3 bond pairs (C-H bonds) and 0 lone pairs.
- Steric number = 3 (bond pairs) + 0 (lone pairs) = 3.
- Hybridization = \( sp^2 \).

**Conclusion**: Change in hybridization from \( sp^3 \) to \( sp^2 \).

### Final Summary
The transformations that involve a change in hybridization are:
- (b) \( BF_3 \) changes from \( sp^2 \) to \( sp^3 \).
- (d) \( PCl_5 \) changes from \( sp^3d \) to \( sp^3 \).
- (e) \( C \) in \( CH_3^+ \) changes from \( sp^3 \) to \( sp^2 \).

### Total Changes in Hybridization
The total number of transformations that involve a change in hybridization is **3**.

---