Question

Change in enthalpy equation help

I am working on calculations for a change in enthalpy/Hess's law experiment, we used calorimeters and reacted 100mL of HCl (in excess) with .152g Mg. Our initial temperature was 20.0C and final temperature was 26.5C. We determined that Ccal for the calorimeter was 56 J/C. How do I determine delta H, the change in enthalpy per mole?

I am currently using the formula

delta H= (mc(Tfinal-Tinitial)+Ccal(Tfinal-Tinitial))/n

Where m = mass

c= specific heat, in this case using 4.184J/g*C (as directed by professor)

and n = number of moles

Does my equation look correct?

I calculated n using the mass of the Mg sample and dividing it by the molar mass of Mg

What do I use as the mass for the experiment?

Do I use the mass of the Mg sample?

The mass of the reactants spent in the reaction? This would be taking the number of moles of Mg present and multiplying it by 2 (since two moles of HCl react with 1 mole of Mg) and the multiplying it by the molar mass of Mg.

Or is it the total mass of the stuff in the calorimeter, so the mass of the Mg sample and the mass of the 100mL of 1.0M HCl?

Help would be appreciated, I've been working on this for 20 hours, most of it trying to figure out what to do, I did try talking to our lab professor but he didn't want to help me.