I gotten this question twice wrong and i dont understand why.

Question

When 1.10 L of 2.10 M  Na2SO4 solution at 30.1°C is added to 1.80 L of 0.700 M  Ba(NO3)2 solution at 30.1°C in a calorimeter, a white solid  forms. The temperature of the mixture increases to 40.1°C. Assuming that the specific heat capacity of the final mixture is 6.37 J/°C⋅g and that its density is 2.00 g/mL, calculate the enthalpy change per mole of BaSO4 formed. Assume that final volume is equal to the sum of initial volumes.

Answer 1

According to the balanced reaction, one mole of Ba(SO₄) is produced for every mole of Ba(NO₃) that reacts. From the given molarities and the volumes of solutions added, you can calculate that 2.31 moles of Na₂(SO₄) and 1.26 moles of Ba(NO₃)₂ are reacting. As the reaction stoichiometry is 1 mole to 1 mole of Na₂(SO₄) and Ba(NO₃)₂, Ba(NO₃)₂ is a limiting reactant, so, only 1.26 moles of Ba(SO₄) is produced. The heat produced by the reaction goes to raising the temperature of the mixture. The relevant equation is ΔH = c x m x Δt where c is the specific heat capacity of the mixture, m is the mass of the final mixture, and Δt the temperature change. the mass can be found from the relation m = DV where D = the density, V is the final volume in mL. Calculate ΔH and divide by 1.26 moles of Ba(SO₄) to get the enthalpy change per mole.

I got 293 kj/mole if I didn't make any math errors.