In a constantpressure calorimeter 600 mL of 0320 M BaOH2 was

In a constant-pressure calorimeter, 60.0 mL of 0.320 M Ba(OH)2 was added to 60.0 mL of 0.640 M HCl. The reaction caused the temperature of the solution to rise from 21.10 °C to 25.46 °C. If the solution has the same density and specific heat as water, what is ΔH for this reaction (per mole of H2O produced)? Assume that the total volume is the sum of the individual volumes.

Solution

Well the heat added to the water would be mass times specific heat x temperature change

Q = mc delta t 120 ml x 4.19 j/goC x 4.5 oC = 2106.732 J or 2.106 kJ

I also checked to make sure that the HCl was in excess and it is so all the Ba(OH)2 is used up.
So you have 0.01815 mol of Ba(OH)2 used up. That will produce 2 x 0.01815 mol of water or 0.0363 mol of water.

So the kJ / mol of water comes to 2.106 kJ / 0.0363 mol of water to get: 58.016 kJ/mol of water.