| Date | May 2010 | Marks available | 1 | Reference code | 10M.2.hl.TZ2.4 |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Comment | Question number | 4 | Adapted from | N/A |
Question
One important property of a rocket fuel mixture is the large volume of gaseous products formed which provide thrust. Hydrazine, N2H4, is often used as a rocket fuel. The combustion of hydrazine is represented by the equation below.
\[\begin{array}{*{20}{l}} {{{\text{N}}_{\text{2}}}{{\text{H}}_{\text{4}}}{\text{(g)}} + {{\text{O}}_{\text{2}}}({\text{g)}} \to {{\text{N}}_{\text{2}}}({\text{g)}} + 2{{\text{H}}_{\text{2}}}{\text{O(g)}}}&{\Delta H_{\text{c}}^\Theta = - {\text{585 kJ}}\,{\text{mo}}{{\text{l}}^{ - 1}}} \end{array}\]
Comment on the environmental safety of the products of the reaction of \({{\text{N}}_{\text{2}}}{{\text{H}}_{\text{4}}}\) with \({{\text{O}}_{\text{2}}}\) and the reaction of \({{\text{N}}_{\text{2}}}{{\text{H}}_{\text{4}}}\) with \({{\text{F}}_{\text{2}}}\).
Markscheme
(\({{\text{N}}_{\text{2}}}\) inert) HF (weak) acid compared to \({{\text{H}}_2}{\text{O}}\) / HF toxic / products of reactions of HF with environment/soil are harmful to environment / OWTTE;
Examiners report
A matter of serious concern is the number of candidates who identified nitrogen as harmful to the environment or a greenhouse gas.
