When 0.969 g of CaO is added to 200.0 mL of 0.500 M HCl(aq), a temperature increase of 397C is observed. Assume the solution's final volume is 200.0 mL, the density is 1.00 g/mL, and the heat capacity is 4.184 J/gC. (Note: Pay attention to significant figures. Do not round until the final answer.) Hrxn , for the reaction of CaO(s) + 2H+(aq) Ca2+(aq) + H2O(l) is kJ/mol.
q = massH2O x heat capacity H2O x delta T.
You have mass water, heat capacity and delta T, calculate q.
That will be q for 0.969 g CaO. Change that to kJ/mol. Post your work if you need further assistance.