Few pairs of molecules are given below. Which bond of the molecule of the pairs is more polar?
(i) `H_(3)C-H,H_(3)C-Br`
(ii) `H_(3)C-NH_(2),H_(3)C-OH`
(iii) `H_(3)C-OH,H_(3)C-SH`
(iv) `H_(3)C-Cl,H_(3)C-SH`

Options

A. `C-Br,C-N,C-O,C-Br`
B. `C-Br,C-O,C-O,C-Cl`
C. `C-Br,C-N,C-S,C-Cl`
D. `C-Br,C-O,C-S,C-Br`

Explanation

To determine which bond in each pair of molecules is more polar, we need to consider the electronegativity of the atoms involved in the bonds. The greater the difference in electronegativity between the two atoms, the more polar the bond will be.

Let's analyze each pair step by step:

### Step 1: Analyze the first pair `H3C-H` and `H3C-Br`
- **Electronegativity of H (Hydrogen)**: 2.1
- **Electronegativity of Br (Bromine)**: 2.8
- **Difference**: 2.8 - 2.1 = 0.7

The C-H bond has a small difference in electronegativity (C is about 2.5), leading to a weakly polar bond. In contrast, the C-Br bond has a larger difference, making it more polar.

**Conclusion**: `H3C-Br` is more polar than `H3C-H`.

### Step 2: Analyze the second pair `H3C-NH2` and `H3C-OH`
- **Electronegativity of N (Nitrogen)**: 3.0
- **Electronegativity of O (Oxygen)**: 3.5
- **Difference**: 3.5 - 2.5 (for C) = 1.0 (for C-O) and 3.0 - 2.5 = 0.5 (for C-N)

The C-O bond is more polar than the C-N bond due to the greater difference in electronegativity.

**Conclusion**: `H3C-OH` is more polar than `H3C-NH2`.

### Step 3: Analyze the third pair `H3C-OH` and `H3C-SH`
- **Electronegativity of S (Sulfur)**: 2.5
- **Difference**: 3.5 - 2.5 = 1.0 (for C-O) and 2.5 - 2.5 = 0.0 (for C-S)

The C-O bond is more polar than the C-S bond, as oxygen is more electronegative than sulfur.

**Conclusion**: `H3C-OH` is more polar than `H3C-SH`.

### Step 4: Analyze the fourth pair `H3C-Cl` and `H3C-SH`
- **Electronegativity of Cl (Chlorine)**: 3.0
- **Difference**: 3.0 - 2.5 = 0.5 (for C-Cl) and 2.5 - 2.5 = 0.0 (for C-S)

The C-Cl bond is more polar than the C-S bond due to the higher electronegativity of chlorine compared to sulfur.

**Conclusion**: `H3C-Cl` is more polar than `H3C-SH`.

### Final Summary:
1. **Pair (i)**: `H3C-Br` is more polar than `H3C-H`.
2. **Pair (ii)**: `H3C-OH` is more polar than `H3C-NH2`.
3. **Pair (iii)**: `H3C-OH` is more polar than `H3C-SH`.
4. **Pair (iv)**: `H3C-Cl` is more polar than `H3C-SH`.