Question

Consider the following reaction: Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
0.103 g of Zn is combined with enough HCl to make 50.0 mL of solution in a coffee-cup calorimeter. As all of the Zn reacts, the temperature of the solution increases from 22.5°C to 23.7°C. Find ΔHrxn (in kJ) for the overall reaction. Assume 1.0 g/mL is the density of the solution and 4.18 J/g°C is the specific heat capacity of the solution.

I know that the equation is ΔHrxn = -qsoln
and
-qsoln = msoln x Cs,soln x ΔT


is m moles or grams? how would you get moles?
Im confused on where to start

Answer 1

msoln is mass of the solution. At a density of 1.0 g/mL, then mass is 50 grams. Use that to determine the q. I think the problem lacks some clarity. dH for the REACTION, I think, is just that -q. You COULD say that dH rxn was -q/0.103 g; however, most problems ask for dH rxn in kJ/mol. So you use -q soln/mols Zn reacted and convert to kJ.