You have been given the task of determining the standard heat of the reaction in which calcium chloride hexahydrate is formed from anhydrous calcium chloride: CaCl₂ (s) + 6 H₂O (l) → CaCl₂ ∙ 6H₂O(s): ΔH˚_г (kJ/mol) = ? By definition, the desired quantity is the heat of hydration of calcium chloride hexahydrate. You cannot carry out the hydration reaction directly, so you resort to an indirect method. You first dissolve 1.00 mol of anhydrous CaCl₂ in 10.0 mol of water in a calorimeter and determine that 64.85kJ of heat must be transferred away from the calorimeter to keep the solution temperature at 25°C. You next dissolve 1.00 mol of the hexahydrate salt in 4.00 mol of water and find that 32.1 kJ of heat must be transferred to the calorimeter to keep the temperature at 25°C.

(a) Use these results to calculate the desired heat of hydration. (Suggestion: Begin by writing out the stoichiometric equations for the two dissolution processes.)

(b) Calculate the standard heat of formation of CaCl₂ (aq, r = 10) in kJ/mol CaCl₂ relative to Ca (s). Cl₂ (g), and H₂O (l) at 25°C