Final answer:
The question involves calculating the enthalpy change for a combustion reaction of dimethylhydrazine in rocket fuel, provided as -1694 kJ. This indicates an exothermic reaction, which can be further understood through stoichiometric calculations that link the moles of a substance with the heat released or absorbed.
Step-by-step explanation:
The question asks to calculate the enthalpy change for the combustion reaction of dimethylhydrazine, which is used as a rocket fuel. The enthalpy change provided is -1694 kJ. To understand how this enthalpy change corresponds to changes in heat during the combustion, we can refer to stoichiometric calculations often used in chemistry.
For example, the combustion of methane releases 890.4 kJ of energy per mole. Therefore, if we react 2 moles of methane, we double the energy release to 1780.8 kJ. Similarly, reacting 0.5 mole of methane releases half of that energy, or 445.2 kJ. This principle can be applied to the combustion reaction in question.
If we were given the amount in moles of dimethylhydrazine used in the reaction, we could utilize these stoichiometric calculations to determine how much heat is released or absorbed during the reaction. The provided enthalpy changes of –1694 kJ suggests that the reaction is exothermic, meaning it releases heat to the surroundings.