Question

A calorimeter contains 18.0 mL of water at 15.0 degrees Celcius . When 1.80 g of X (a substance with a molar mass of 42.0 g/mol) is added, it dissolves via the reaction X(s)+H2O(l)-->X(aq) and the temperature of the solution increases to 30.0 degrees Celcius . 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. Express the change in enthalpy in kilojoules per mole to three significant figures.