Question

In an experiment liquid hexane, C6H14 (l) is combusted completely to produce CO2(g) and H2O (l) according to the equation:

2 C6H14 (l) + 19 O2(g) -> 12 CO2(g) + 14H2O (l)

The change in H degrees for the reaction is -8.39 x 10^3 KJ. Calculate change in H degrees for C6H14 (l).

Answer 1

AAARRRGGGG. H with a little circle at the top right is NOT degrees.

I will shift to more conventional symbols

Hr (heat of reaction,or reaction enthalpy)= -8.39E3 KJ
Hcombustion= -4.25 kJ/mole

Notice the units for heat of combustion. It is commonly on a per mole basis, but can be on a per mass, or per volume basis. Heats of reaction are usually in heat units, based on the reaction, but it is not unusual to find them in a per mole or per gram basis. In this instance, I assumed from the wording it was based on the amounts in moles of the coefficents. Better wording would have been desired.