When 40.0 mL of 0.200 M HCl at 21.5°C is added to 40.0 mL of 0.200 M NaOH also at 21.5°C in a coffee-cup calorimeter, the temperature of the resulting solution rises to 22.8°C. Assume that the volumes are additive, the specific heat of the solution is 4.18 Jg-1°C-1 and that the density of the solution is 1.00 g mL-1 Calculate the enthalpy change, ?H in kJ for the reaction: HCl(aq) + NaOH(aq) => NaCl(aq) + H2O(l)