State and explain the difference in bond strength between the nitrogen atoms in a hydrazine and nitrogen molecule.

State why hydrazine has a higher boiling point than dinitrogen tetraoxide.

Determine the oxidation state of nitrogen in the two reactants.

Deduce, giving a reason, which species is the reducing agent.

Deduce the Lewis (electron dot) structures of ozone.

triple bond in nitrogen «molecule» AND single bond in hydrazine

triple bond stronger than single bond
OR
more shared «pairs of» electrons make bond stronger/attract nuclei more

Accept bond enthalpy values from data booklet (158 and 945 kJ\(\,\)mol^–1).

[2 marks]

hydrogen bonding «between molecules, dinitrogen tetraoxide does not»

[1 mark]

N₂H₄: –2 AND N₂O₄: +4

[1 mark]

N₂H₄ AND oxidized/oxidation state increases
OR
N₂H₄ AND loses hydrogen
OR
N₂H₄ AND reduces/removes oxygen from N₂O₄

Accept “N₂H₄ AND gives electrons «to N₂O₄»”.

[1 mark]

Accept any combination of lines, dots or crosses to represent electrons.

Do not penalize missing lone pairs if already done in 3b.

Do not accept structure that represents 1.5 bonds.

[2 marks]