Question

A calorimeter contains 18.0 mL of water at 12.0\, ^{\circ}C. When2.50 g of \rm X (a substance with a molar mass of 69.0 g/mol) isadded, it dissolves via the reaction

\rm X{(s)}+H_2O{(l)} \rightarrow X{(aq)}
and the temperature of the solution increases to 27.0\,^{\circ}C.

Calculate the enthalpy change, Delta H, for this reaction per moleof \rm X.

Assume that the specific heat and density of the resulting solutionare equal to those of water [4.18 \rm J/(g \cdot {^\circ C}) and1.00 \rm g/mL] and that no heat is lost to the calorimeter itself,nor to the surroundings.