Mg+2HCl=MgCl2+H2
When 1.50 grams of magnesium is combined with 100.0mL of HCL to make 101.5mL of solution in a coffee-cup calorimeter, all of the magnesium reacts, raising the temperature of the solution from 22.5 degrees Celsius to 27.7 degrees Celsius. Find Delta Hrxn for this reaction. The formula is Q=m x Cs x delta T.
I prefer to space the equation to a more readable form:
Mg + 2HCl ==> MgCl2 + H2
Frankly, I don't understand what trouble you're having. Just plug in the numbers.
q = mc*dT = 101.5 g x 4.184 J/g*c x (27.7 - 22.5) = 2208.3 J so I would say dHrxn = 2208.3 J. USUALLY the problem asks for dH in kJ/mol.