Chemical energetics: describe question

The reaction between hydrogen and iodine is shown.

$$\ce{H2(g) + I2(g) -> 2HI(g)} \quad \Delta H = +26 \text{ kJ mol}^{-1}$$

Some average bond energies are:

• H–H: 436 kJ mol$^{-1}$
• I–I: 151 kJ mol$^{-1}$
• H–I: 299 kJ mol$^{-1}$

Describe the energy changes that take place during this reaction. In your answer you should:

• explain the roles of bond breaking and bond making in determining the enthalpy change of the reaction,
• discuss the interpretation of the enthalpy change and the activation energy on a reaction pathway diagram,
• explain why the enthalpy change calculated using the average bond energies differs from the given value,
• state the meaning of standard enthalpy change of reaction and how it differs from standard enthalpy change of formation.