The H-C-H bond angle in `CH_(4) is 109.5^(@)`, due to lone pair repulsion, the H-O-H angle in `H_(2)O` will :

Options

A. remain the same
B. increase
C. decrease
D. become `180^(@)`

Answer

To determine how the H-O-H bond angle in H₂O is affected by lone pair repulsion, we can follow these steps:

### Step 1: Understand the VSEPR Theory
The Valence Shell Electron Pair Repulsion (VSEPR) theory states that electron pairs around a central atom will arrange themselves to minimize repulsion. This includes lone pairs and bond pairs.

**Hint:** Remember that lone pairs take up more space than bonding pairs, affecting bond angles.

### Step 2: Analyze the Structure of CH₄
In methane (CH₄), the carbon atom is bonded to four hydrogen atoms. Since there are no lone pairs on the carbon atom, the molecule adopts a tetrahedral shape with bond angles of 109.5°.

**Hint:** Identify the number of lone pairs and bond pairs in the molecule to predict the geometry.

### Step 3: Analyze the Structure of H₂O
In water (H₂O), the oxygen atom has two lone pairs and forms two bonds with hydrogen atoms. The presence of these lone pairs will influence the bond angle.

**Hint:** Count the lone pairs on the central atom (oxygen) and how they might affect the bond angles.

### Step 4: Consider Lone Pair Repulsion
According to VSEPR theory, lone pair-lone pair repulsion is stronger than lone pair-bond pair repulsion, which in turn is stronger than bond pair-bond pair repulsion. The two lone pairs on oxygen will repel each other and also push the hydrogen atoms closer together.

**Hint:** Recall that lone pairs exert a greater repulsive force than bonding pairs, which will compress the bond angle.

### Step 5: Conclusion on H-O-H Bond Angle
Due to the repulsion from the two lone pairs, the H-O-H bond angle in water is less than the tetrahedral angle of 109.5°. It is approximately 104.5°.

**Hint:** Think about how the presence of lone pairs alters the expected bond angles based on the geometry of the molecule.

### Final Answer
The H-O-H bond angle in H₂O will decrease due to lone pair repulsion, leading to an angle of approximately 104.5°.