A calorimeter contains 27.0 g of water at 11.0 C. When 2.10 g of X (a substance with a molar mass of 80.0 g) is added, it dissolves via the reaction
X (s) +H2O (l) -> X (aq)
and the temperature of the solution increases to 25.0 C.
Calculate the enthalpy change, , for this reaction per mole of X.
Assume that the specific heat and density of the resulting solution are equal to those of water [4.18 J/ g.C and 1.00 g/mL ] and that no heat is lost to the calorimeter itself, nor to the surroundings.