Alright so I have to finish up an Enthalpy reaction. We did experiments in class and constructed chemical equations. The question is: find the heat of combustion of Magnesium.
So all I need to know to actually finish that question is what it actually means....
![Tongue :P](https://www.chemicalforums.com/Smileys/classic/tongue.gif)
I'm trying to set up an equation that shows the beginning of the reaction and the end.
What i have is Mg + O
2g = MgO[/s][/s]
Okay, and here are my other equations
MgCl2 +
H2O ---> MgO +
2HCl H = 0.4184 kJ
2HCl + Mg ------------>
H2 +
MgCl2 H =-1.338 kJ
H2[/sub] + 1/2O
2 ------->
H2O H = -285.8 kJ
My experimental heat of combustion per mol is -286.720
This is horribly wrong, with a percent error of more than 50%. The real enthalpy value is -601.6 kJ
Does anyone see what I could've done wrong? I used Hess's law, which states the steps of individual reactions adds up to the total reaction. Maybe my equatoins aren't balanced and i don't realize it?