A calorimeter contains 18.0 mL of water at 11.5 ∘C . When 2.40 g of X (a substance with a molar mass of 52.0 g/mol ) is added, it dissolves via the reaction X(s) H2O(l)→X(aq) and the temperature of the solution increases to 26.0 ∘C . Calculate the enthalpy change, ΔH , for this reaction per mole of X . Assume that the specific heat of the resulting solution is equal to that of water [4.18 J/(g⋅∘C) ], that density of water is 1.00 g/mL , and that no heat is lost to the calorimeter itself, nor to the surroundings. Express the change in enthalpy in kilojoules per mole to three significant figures.