Enthalpy change (1 Viewer)

[Octavius]

I have some questions

Is the heat of combustion the same as enthalpy change?

What are the formula for enthalpy change and heat of combustion?
I have seen that you use q=mc(delta)t and then use delta h = q/n to find enthalpy change. I have also seen that you use this same formula for the heat of combustion. I don't get how this works because shouldn't there be a negative sign along the way in one of the equations?

 

[LennonTheLemon]

Your thinking is correct. The formula q = mcΔT gives you the heat energy released (this can be positive or negative depending on the value of ΔT). The formula for enthalpy change is actually ΔH = -q/n which means that when you put in a q value >0 you will get a negative ΔH. This makes sense because it indicates that heat is lost from the system. If q<0 (this would happen in an endothermic reaction), then ΔH will be positive which indicates that heat energy is absorbed into the system.