The compound with highest boiling point is :

Options

A. `C_2H_5I`
B. `C_2H_5Br`
C. `C_2H_5Cl`
D. `CH_3Cl`

Explanation

To determine which compound has the highest boiling point among the given options, we can follow a systematic approach based on the principles of boiling point determination.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We have four compounds to consider:
- A: C2H5I (Ethyl iodide)
- B: C2H5Br (Ethyl bromide)
- C: C2H5Cl (Ethyl chloride)
- D: C2H5F (Ethyl fluoride)

2. **Understand the Factors Affecting Boiling Point**:
The boiling point of a compound is influenced by two main factors:
- **Molecular Weight**: Higher molecular weight generally leads to a higher boiling point.
- **Branching**: More branching in the molecular structure typically results in a lower boiling point.

3. **Compare Molecular Weights**:
- Calculate the molecular weights of each compound:
- C2H5I: (2*12) + (5*1) + (1*127) = 24 + 5 + 127 = 156 g/mol
- C2H5Br: (2*12) + (5*1) + (1*80) = 24 + 5 + 80 = 109 g/mol
- C2H5Cl: (2*12) + (5*1) + (1*35.5) = 24 + 5 + 35.5 = 64.5 g/mol
- C2H5F: (2*12) + (5*1) + (1*19) = 24 + 5 + 19 = 48 g/mol

4. **Analyze the Halogen Influence**:
- The boiling point is also affected by the type of halogen:
- Iodine (I) has the highest atomic mass, followed by bromine (Br), chlorine (Cl), and fluorine (F).
- Since C2H5I has iodine, it will have a higher boiling point compared to C2H5Br, C2H5Cl, and C2H5F.

5. **Determine the Order of Boiling Points**:
- Based on molecular weights and halogen types, we can establish the order of boiling points:
- C2H5I > C2H5Br > C2H5Cl > C2H5F

6. **Conclusion**:
- The compound with the highest boiling point is C2H5I (Ethyl iodide).

### Final Answer:
The compound with the highest boiling point is **C2H5I** (Ethyl iodide).

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