question_answer

Which of the following combustion reactions would give maximum energy output per unit mass fuel plus oxidant when used to propel a rocket?

A) \[C(s)+{{O}_{2}}\xrightarrow{{}}C{{O}_{2}}(g),\,\,\Delta H=-394\,KJ/mol\]

B) \[{{H}_{2}}(g)+\frac{1}{2}{{O}_{2}}\xrightarrow{{}}{{H}_{2}}O(l),\,\Delta H=-285\,kJ/mol\]

C) \[\frac{1}{2}{{H}_{2}}+\frac{1}{2}{{F}_{2}}\xrightarrow{{}}2HF(g),\,\Delta H=-271\,kJ/mol\]

D) \[C{{H}_{4}}+2{{O}_{2}}\xrightarrow{{}}C{{O}_{2}}(g)+2{{H}_{2}}O(l),\]\[\Delta H=-890\,kJ/mol\]