Heat of combustion (1 Viewer)

[iStudent]

In our final answer do we write it as negative or not?
I'm getting conflicting answers from sample answers textbook and internet sources :s

 

[faisalabdul16]

If it's an exothermic reaction, delta h = negative
If it's an endothermic reaction, delta h = positive
If it's molar heat of combustion it's positive for both

 

[DepressedPenguino]

^ believe him

 

[QZP]

Heat of combustion is always a positive value

 

[iStudent]

Is there ever a time when we have to make our final answer negative? (in one of those e.g. ethanol questions requiring you to use q=mcat)

 

[QZP]

Is there ever a time when we have to make our final answer negative? (in one of those e.g. ethanol questions requiring you to use q=mcat)

Depends how they word it. Are they asking you for the molar heat of combustion or change in enthalpy? If neither, then be safe and just say "molar heat of combustion: {some positive value}" or alternatively "delta H = {some positive/negative value accordingly}"