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The bond energy (D or ΔHdissociation) is 190 kJ for 1 mol of Br―Br bonds, and 155 kJ for 1 mol of F―F bonds. The heat of vaporization of bromine is + 30.0 kJ/mol, and the standard heat of formation (ΔH°f ) of BrF3(g) is -256 kJ/mol.

a)Write the chemical equation which corresponds to the standard heat of formation of BrF3(g).

b)Write and balance the chemical reactions involved in the processes, and when the terms cancel out.

c)Determine the average energy for a Br – F bond, in kJ/mol. Show your calculations.


I'm not sure how to start this. It's a question from last year's exam. Been looking through books for a while now. Any help appreciated.

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I have 1/2 Br2 + 3/2 F2 --->BrF3

Not sure if that is correct for a

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For c) since there are three B-F bonds do I just divide the 256 by 3?