6 3 Nitrogen forms several hydrides. In addition to ammonia, NH3 , it forms hydrazine, N2H4 , in which the two nitrogen atoms are covalently bonded together. (a) (i) Explain what is meant by a covalent bond. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (ii) Draw a dot‑and‑cross diagram for hydrazine, showing the outer electrons only. Use crosses (×) to represent the electrons from nitrogen and dots ( • ) to represent the electrons from hydrogen. (1) (iii) Estimate the H N H bond angle in hydrazine. (1) Bond angle = .............................................................. 7 Turn over (b) Hydrazine is very soluble in water. Explain, using a labelled diagram and naming the relevant intermolecular interactions, why hydrazine is very soluble in water. 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(c) Hydrazine has been used as a rocket fuel. It is a powerful reducing agent and will react very exothermically with oxidising agents such as hydrogen peroxide. The equation for the reaction of hydrazine with hydrogen peroxide is N2H4(l) + 2H2O2(l) → N2(g) + 4H2O(g) Give two reasons why hydrazine is a good rocket fuel when reacted with hydrogen peroxide. 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(Total for Question 3 = 9 marks)