Bmat 2018 q 26 chemistry

answer: C
can someone explain? thanks


  1. Xenon gas reacts with fluorine gas to form xenon hexafluoride. The chemical reaction can be represented as:
    Xe + 3F2 → XeF6
  2. Overall energy change, ΔH, is -330 kJ/mol.
  3. The F-F bond energy is 158 kJ/mol.

To find:
The Xe-F bond energy.

The overall energy change in the reaction is the difference between the energy required to break the bonds and the energy released when new bonds are formed.

  1. Calculate the total energy required to break the F-F bonds. There are 3 moles of F2, so 3 F-F bonds need to be broken.
    Energy required to break 3 F-F bonds = 3 x F-F bond energy

  2. Let the Xe-F bond energy be x. Since there are 6 Xe-F bonds in xenon hexafluoride, the energy released when these bonds are formed is 6x.

  3. From the overall energy change, we can form the following equation:
    Energy required to break bonds - Energy released when new bonds are formed = ΔH
    3 x 158 kJ/mol - 6x = -330 kJ/mol

Solving for x, we get:
x = 134 kJ/mol