Multiple Choice
Use the bond energies in Chemistry 2e of your textbook to determine the approximate enthalpy change for the following reaction: H2(g) + 1/2 O2(g) → H2O(g). What is the approximate enthalpy change (ΔH) for this reaction?
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11. Bonding & Molecular Structure
Bond Energy
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Using the bond energies provided, estimate the ΔH°rxn for the reaction: XeF2 + 2 F2 → XeF6.
A
+176 kJ
B
-429 kJ
C
+159 kJ
D
-270 kJ
Verified step by step guidance1
Identify the bonds broken and formed in the reaction. In the reaction XeF2 + 2 F2 → XeF6, the bonds broken are 2 Xe-F bonds in XeF2 and 2 F-F bonds in F2. The bonds formed are 6 Xe-F bonds in XeF6.
Use the bond energies provided to calculate the total energy required to break the bonds. This involves multiplying the bond energy of each type of bond by the number of such bonds broken.
Calculate the total energy released by forming the new bonds. This involves multiplying the bond energy of each type of bond by the number of such bonds formed.
Apply Hess's Law to estimate the ΔH°rxn. This is done by subtracting the total energy released (from bond formation) from the total energy required (from bond breaking).
Combine the calculated values to estimate the ΔH°rxn for the reaction. Remember that a negative value indicates an exothermic reaction, where more energy is released than absorbed.
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