Which halide does not exist in a gaseous state at ordinary temperature?

Options

A. `CH_(3)`Cl
B. `C_(2)H_(5)`Cl
C. `CH_(3)`l
D. `CH_(3)`Br

Answer

To determine which halide does not exist in a gaseous state at ordinary temperature, we need to analyze the molecular masses of the given compounds and their corresponding intermolecular forces.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are:
- CH3Cl (Methyl chloride)
- C2H5Cl (Ethyl chloride)
- CH3I (Methyl iodide)
- CH3Br (Methyl bromide)

2. **Understand the Concept of Molecular Mass**: The molecular mass of a compound influences its physical state at a given temperature. Generally, compounds with higher molecular masses have stronger van der Waals forces (dispersion forces) due to increased electron cloud size, leading to greater intermolecular attraction.

3. **Calculate the Molecular Masses**:
- **CH3Cl**:
- C: 12 g/mol
- H: 3 × 1 g/mol = 3 g/mol
- Cl: 35.5 g/mol
- Total = 12 + 3 + 35.5 = 50.5 g/mol
- **C2H5Cl**:
- C: 2 × 12 g/mol = 24 g/mol
- H: 5 × 1 g/mol = 5 g/mol
- Cl: 35.5 g/mol
- Total = 24 + 5 + 35.5 = 64.5 g/mol
- **CH3I**:
- C: 12 g/mol
- H: 3 × 1 g/mol = 3 g/mol
- I: 127 g/mol
- Total = 12 + 3 + 127 = 142 g/mol
- **CH3Br**:
- C: 12 g/mol
- H: 3 × 1 g/mol = 3 g/mol
- Br: 80 g/mol
- Total = 12 + 3 + 80 = 95 g/mol

4. **Compare the Molecular Masses**:
- CH3Cl: 50.5 g/mol
- C2H5Cl: 64.5 g/mol
- CH3Br: 95 g/mol
- CH3I: 142 g/mol

5. **Identify the Compound with the Highest Molecular Mass**: From the calculations, CH3I has the highest molecular mass (142 g/mol).

6. **Determine the Physical State**: Due to its high molecular mass, CH3I will have stronger van der Waals forces, which means it is less likely to exist in the gaseous state at ordinary temperatures. Instead, it is expected to exist in the liquid state.

7. **Conclusion**: Therefore, the halide that does not exist in a gaseous state at ordinary temperature is **CH3I**.

### Final Answer:
**CH3I (Methyl iodide)** does not exist in a gaseous state at ordinary temperature.