Question

$Xe{F}_{2\left(g\right)}+H_2\left(g\right)\to 2H{F}_{\left(g\right)}+X{e}_{\left(g\right)},\Delta H^o=-430kJ$

Bond energy $\to H-H=435kJ/mol\to H-F=565kJ/mol$
Calculate average bond energy of $Xe-F$ bond.

• A. $265kJ/mol$
• B. $562.5kJ/mol$
• C. $132.5‘kJ/mol$
• D. None of these

Answer 1

Answer: (C)

$132.5‘kJ/mol$

$Xe{F}_2\left(g\right)+H_2\left(g\right)⟶2HF\left(g\right)+Xe\left(g\right)$ $\Delta H^o=-430KJ$

This reaction contains,

$\Delta H_1=2\times$ Bond dissocition energy of $Xe-F=2\times xKJ/mol$

$\Delta H_2=1\times$ Bond dissociation energy of $H-H=435KJ/mol$

$\Delta H_3=2\times$ Bond formation energy of $H-F=2\times (-565)KJ/mol$

Thus $\Delta H_1+\Delta H_2+\Delta H_2=\Delta H$

$\Rightarrow 2\times x+435+2\times (-565)KJ/mole=-430KJ/mole$

$\Rightarrow 2x=265KJ/mole$

or $\Rightarrow x=132.5KJ/mole$

Thus average bond energy of $Xe-F$ bond is $132.5KJ/mole$