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Which one of the following orders is not in accordance with the property stated against it?
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Verified Answer
The correct answer is:
$\mathrm{F}_2>\mathrm{Cl}_2>\mathrm{Br}_2>\mathrm{I}_2$ : bond dissociation energy
Bond dissociation energy of halogen family decreases down the group as the size of atom increases. The decreasing order for the bond dissociation enthalpy of halogen molecules is
$\mathrm{Cl}_2(57 \mathrm{kcal} / \mathrm{mol})>\mathrm{Br}_2(45.5 \mathrm{kcal} /$ $\mathrm{mol})>\mathrm{F}_2(38 \mathrm{kcal} / \mathrm{mol})>\mathrm{I}_2(35.6$ $\mathrm{kcal} / \mathrm{mol}$ ).
A Caution
A halogen molecule having larger atoms should have low dissociation energy and vice versa. Fluorine is an exception because of interelectronic repulsion is present in small atom of fluorine
$\mathrm{Cl}_2(57 \mathrm{kcal} / \mathrm{mol})>\mathrm{Br}_2(45.5 \mathrm{kcal} /$ $\mathrm{mol})>\mathrm{F}_2(38 \mathrm{kcal} / \mathrm{mol})>\mathrm{I}_2(35.6$ $\mathrm{kcal} / \mathrm{mol}$ ).
A Caution
A halogen molecule having larger atoms should have low dissociation energy and vice versa. Fluorine is an exception because of interelectronic repulsion is present in small atom of fluorine
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