Multiple Choice
Using the bond energies provided, estimate the standard enthalpy change (ΔH°rxn) for the reaction: XeF2 + 2 F2 → XeF6.
11. Bonding & Molecular Structure
Bond Energy
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Given that the enthalpy change (ΔH) for the formation of H2O(g) from its elements is -926.29 kJ/mol, what is the approximate bond energy of the O-H bond in water?
A
463 kJ/mol
B
1852 kJ/mol
C
231 kJ/mol
D
926 kJ/mol
Verified step by step guidance1
Understand that the enthalpy change (ΔH) for the formation of water vapor (H2O(g)) from its elements involves breaking and forming bonds. The reaction can be represented as: H2(g) + 1/2 O2(g) → H2O(g).
Recognize that the enthalpy change given (-926.29 kJ/mol) is for the formation of one mole of water vapor from its elements in their standard states.
Recall that the bond energy is the energy required to break one mole of a bond in a gaseous substance. For water, the O-H bond energy is the energy needed to break the O-H bonds in H2O(g).
Since water has two O-H bonds, the total energy required to break both O-H bonds in one mole of water is twice the bond energy of a single O-H bond.
To find the bond energy of a single O-H bond, divide the total enthalpy change for the formation of water by 2, as there are two O-H bonds in each water molecule.
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