Question

Assertion (A): The boiling points of alkyl halides decrease in the order: RI>RBr>RCl>RF. 
Reason (R): The boiling points of alkyl chlorides, bromides and iodides are considerably higher than that of the hydrocarbon of comparable molecular mass.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Boiling points of alkyl halides are influenced by the size of the halogen and the intermolecular forces present.

Answer 1

The Correct Option is C

Order of Boiling Points for Alkyl Halides

Step 1: Boiling Point Trend. The boiling points of alkyl halides follow the trend: \( \text{RI} > \text{RBr} > \text{RCl} > \text{RF} \). This is due to the increasing size of the halogen atom from fluorine to iodine, which results in stronger dispersion forces and thus higher boiling points.

Step 2: Rationale for the Trend. The assertion that alkyl halides exhibit higher boiling points than hydrocarbons of similar molecular mass is correct. However, this fact does not explain the specific order of boiling points among the alkyl halides. The primary factor determining this order is the halogen's atomic size and the resulting intermolecular forces.

Step 3: Summary. Both the assertion and the provided reason are factually correct. Nevertheless, the reason does not adequately explain the assertion. The correct selection is option (B).