5.3 Bond Enthalpy

Methane reacts violently with fluorine to form carbon tetrafluoride and hydrogen fluoride

Formulate the equation for this reaction. 

[2]

Use your answer to part a) and section 10 of the data booklet to calculate the following:

The energy required, in kJ, to break the bonds for the reaction between methane and fluorine.

[1]

The energy released, in kJ, to form the bonds for the reaction between methane and fluorine.

[1]

The enthalpy change, ΔH_r, in kJ mol^-1 for this reaction. 

[2]

A student suggested that one reason for the high reactivity of fluorine is a weak F−F bond. State whether the student is correct. Justify your answer. 

[2]

Sketch a labelled energy diagram for the reaction of methane and fluorine.

[3]

Hydrazine has the formula N₂H₄ and is used as a rocket fuel (e.g. for the Apollo moon rockets). It burns in the following reaction for which the enthalpy change is -583 kJ mol^-1.

N₂H₄ (g) + O₂ (g) → N₂ (g) + 2H₂O (g)

Sketch the Lewis structure of hydrazine, N₂H₄.

[2]

Use section 11 of the Data booklet and the information in part a) to deduce the bond enthalpy, in kJ mol^-1, for the N-N bond.

[3]

Outline why the value of enthalpy of reaction calculated from bond enthalpies is less accurate.

[1]

By using equations, state the environmental impact of CFCs on the ozone layer.