JEE Main · 2005 · 08 May 2005 · Offline · p-Block Elements

The correct order of the thermal stability of hydrogen halides

(H - X)

(A) $HI > HBr > HCl > HF$
(B) $HF > HCl > HBr > HI$ ✓ Correct
(C) $HCl < HF > HBr < HI$
(D) $HI > HCl < HF < HBr$

Answer: (B)

Solution

Thermal stability of a hydrogen halide reflects the strength of the

H - X

bond, and that bond weakens as the halogen grows larger and its overlap with hydrogen's small

1 s

orbital worsens. Fluorine, the smallest, forms the strongest and most heat-resistant bond, and stability then falls steadily down the group, giving the order

HF > HCl > HBr > HI

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option

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