The correct order of boiling points is

Options

A. `CH_(3)F lt CH_(3)Cl lt CH_(3)Br lt CH_(3)I`
B. `CH_(3)F lt CH_(3)I lt CH_(3)Br lt CH_(3)Cl`
C. `CH_(3)I lt CH_(3)Br lt CH_(3)Cl lt CH_(3)F`
D. `CH_(3)F lt CH_(3)Br lt CH_(3)Cl lt CH_(3)I`

Answer

To determine the correct order of boiling points for haloalkanes (alkyl halides), we need to consider the factors that influence boiling points, particularly the molecular weight and surface area of the compounds involved. Here’s a step-by-step solution:

### Step 1: Understand the Factors Affecting Boiling Points
The boiling point of a substance is influenced by the strength of intermolecular forces. In the case of haloalkanes, the primary intermolecular forces are Van der Waals forces (dispersion forces), which depend on:
- Molecular weight (mass)
- Surface area of the molecules

### Step 2: Analyze the Given Elements
We need to compare the boiling points of haloalkanes containing different halogens (F, Cl, Br, I). The molecular weights of these halogens are:
- Fluorine (F): 19 g/mol
- Chlorine (Cl): 35.5 g/mol
- Bromine (Br): 80 g/mol
- Iodine (I): 127 g/mol

### Step 3: Consider the Alkyl Group
We will consider the alkyl group (e.g., CH3) attached to the halogen. The general formula for the haloalkanes we are comparing would be CH3X, where X is the halogen.

### Step 4: Determine the Mass Order
The mass order of the halogens is:
- CH3F < CH3Cl < CH3Br < CH3I
This order is based on the increasing molecular weight of the halogens.

### Step 5: Relate Mass to Boiling Point
Since boiling points increase with increasing molecular weight due to stronger Van der Waals forces, we can conclude:
- CH3I will have the highest boiling point.
- CH3Br will have a lower boiling point than CH3I but higher than CH3Cl.
- CH3Cl will have a lower boiling point than CH3Br but higher than CH3F.
- CH3F will have the lowest boiling point.

### Step 6: Final Order of Boiling Points
Thus, the correct order of boiling points from lowest to highest is:
**CH3F < CH3Cl < CH3Br < CH3I**

### Conclusion
The correct order of boiling points is CH3F < CH3Cl < CH3Br < CH3I.

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