Because the prac that you did on it is an essential prac and they can ask you about it in the HSC.
Yeah about how and why experimental values differ from theoretic values:
- we assume complete combustion but you can see soot forming at the base of the beaker
- our heating methods were not 100% efficient because some heat could have been lost to the air.
Other things molar heat of combustion is useful for is for comparing ethanol and octane as a fuel:
ethanol is 1364Kj/mol and octane is 5467kJ/mol.