Bond angle in dimethyl ether is more than that in water.

Answer

To understand why the bond angle in dimethyl ether is greater than that in water, we can analyze the molecular structures and hybridization of both compounds step by step.

### Step 1: Identify the Molecular Structures
- **Dimethyl Ether (CH3-O-CH3)**: This molecule consists of two methyl groups (CH3) attached to an oxygen atom.
- **Water (H2O)**: This molecule consists of two hydrogen atoms bonded to an oxygen atom.

**Hint**: Start by drawing the structural formulas of both compounds to visualize their shapes.

### Step 2: Determine Hybridization
- **Dimethyl Ether**: The central atom (oxygen) is bonded to two carbon atoms and has no lone pairs. The hybridization of oxygen in dimethyl ether is **sp³**.
- **Water**: The central atom (oxygen) is bonded to two hydrogen atoms and has two lone pairs. The hybridization of oxygen in water is also **sp³**.

**Hint**: Recall that hybridization can be determined by counting the number of sigma bonds and lone pairs around the central atom.

### Step 3: Calculate Steric Number
- **Steric Number for Dimethyl Ether**:
- Number of sigma bonds = 2 (C-O bonds)
- Number of lone pairs = 0
- Steric number = 2 + 0 = 2
- **Steric Number for Water**:
- Number of sigma bonds = 2 (O-H bonds)
- Number of lone pairs = 2
- Steric number = 2 + 2 = 4

**Hint**: The steric number helps determine the geometry of the molecule, which influences bond angles.

### Step 4: Analyze Molecular Geometry
- **Dimethyl Ether**: With a steric number of 2, the geometry is **linear**, leading to a bond angle of approximately **120°**.
- **Water**: With a steric number of 4, the geometry is **tetrahedral**, but due to the presence of two lone pairs, the shape is **bent** (V-shaped), resulting in a bond angle of about **104.5°**.

**Hint**: Consider how lone pairs occupy more space and repel bonding pairs, affecting the bond angles.

### Step 5: Compare Bond Angles
- The bond angle in dimethyl ether (approximately 120°) is greater than the bond angle in water (approximately 104.5°). This difference arises because:
- In dimethyl ether, there are no lone pairs on the central atom to create additional repulsion.
- In water, the two lone pairs exert more repulsion on the bonding pairs, reducing the bond angle.

**Hint**: Use the VSEPR theory to explain how electron pair repulsion affects bond angles.

### Conclusion
Thus, the bond angle in dimethyl ether is greater than that in water due to the absence of lone pairs on the oxygen in dimethyl ether, leading to less repulsion between bonding pairs compared to water.