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NEET CHEMISTRYHaloalkanes and HaloarenesEasy

Question

Find the correct sequence of the bond enthalpy of the C-X\text{C-X} bond among the following:

A

CH3-F>CH3-Br>CH3-Cl>CH3-I\text{CH}_3\text{-F} > \text{CH}_3\text{-Br} > \text{CH}_3\text{-Cl} > \text{CH}_3\text{-I}

B

CH3-Cl>CH3-F>CH3-Br>CH3-I\text{CH}_3\text{-Cl} > \text{CH}_3\text{-F} > \text{CH}_3\text{-Br} > \text{CH}_3\text{-I}

C

CH3-F>CH3-Cl>CH3-Br>CH3-I\text{CH}_3\text{-F} > \text{CH}_3\text{-Cl} > \text{CH}_3\text{-Br} > \text{CH}_3\text{-I}

D

CH3-I>CH3-Br>CH3-Cl>CH3-F\text{CH}_3\text{-I} > \text{CH}_3\text{-Br} > \text{CH}_3\text{-Cl} > \text{CH}_3\text{-F}

Step-by-Step Solution

As we move down the halogen group in the periodic table, the size of the halogen atom increases from fluorine to iodine. Consequently, the carbon-halogen (C-X\text{C-X}) bond length increases from C-F\text{C-F} to C-I\text{C-I} . Since bond enthalpy is inversely proportional to bond length, the bond enthalpy decreases as the bond length increases. According to standard data, the bond enthalpies are: CH3-F\text{CH}_3\text{-F} (452 kJ/mol), CH3-Cl\text{CH}_3\text{-Cl} (351 kJ/mol), CH3-Br\text{CH}_3\text{-Br} (293 kJ/mol), and CH3-I\text{CH}_3\text{-I} (234 kJ/mol) . Thus, the correct decreasing order of bond enthalpy is CH3-F>CH3-Cl>CH3-Br>CH3-I\text{CH}_3\text{-F} > \text{CH}_3\text{-Cl} > \text{CH}_3\text{-Br} > \text{CH}_3\text{-I}.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Haloalkanes and Haloarenes. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYHaloalkanes and Haloarenescorrectsequenceenthalpytextcxfollowing

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