How to Calculate the Enthalpy of Combustion of a Molecule – Part 1

The enthalpy of combustion of a substance, usually a fuel/food, is the amount of enthalpy/heat/energy released (in calorie/Joule) during the combustion/burning of a given amount of it.


The enthalpy of combustion always has a negative value (exothermic reaction).

Question:

2CH6N2(l) + 5O2(g) → 2N2(g) + 2CO2(g) + 6H2O(g)

The combustion of Methylhydrazine, a common rocket fuel, is represented above. ΔHr = –1303 kJ mol−1. What would be the ΔH per mol of CH6N2(l) if the reaction produced H2O(l) instead of H2O(g)? (ΔH for the condensation of H2O(g) to H2O(l) = –44 kJ mol−1)

Solution:



Click to enlarge the image

Is it challenging to recall that the enthalpy of reaction is per mole❓ Let Chemaficionado know at mychemistryhomework@gmail.com❗

References:

(1)    Wikipedia Contributors. Heat of combustion. Wikipedia. https://en.wikipedia.org/wiki/Heat_of_combustion.

‌(2)    Ncert. Chemistry : Textbook for Class XI - Part.I; National Council Of Educational Research And Training: New Delhi.

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