Write the equation for the dissociation of HF into H and F atoms. Classify the reaction as endothermic or exothermic, and give the AH value for the reaction.

Question

Note: Reference the Bond energies table for additional information.

kcal
mol

Bond

H-H

F-F

C1-C1

Br-Br

I-I

H-OH

H-F

H-C1

H-Br

H-I

energy

+104

+38

+58

+46

+36

+119

+136

+103

+87

+71

Write the equation for the dissociation of HF into H and F atoms.

Answer 1

HF -> H + F

This reaction is endothermic because bonds are being broken in the reactant molecule to form the products. The AH value for the reaction can be calculated by adding the bond energies of the bonds broken in HF and subtracting the bond energy of the bond formed in H2.

AH = +136 + 103 - 136 = +103 kcal/mol