Question

Calculate the heat of crystallization of 5 moles of calcium chloride, given that the enthalpy change of hydration of calcium ions is –1622 kJ/mol and that of chloride ions is –364 kJ/mol.

Answer 1

To calculate the heat of crystallization of 5 moles of calcium chloride  CaCl , we need to consider the enthalpy changes of hydration for both calcium ions  Ca  and chloride ions  Cl .Calcium chloride dissociates into one calcium ion and two chloride ions in solution:CaCl  Ca + 2ClFor 1 mole of calcium chloride, the enthalpy change of hydration will be:H =  1  H_hydration Ca   +  2  H_hydration Cl  Given that the enthalpy change of hydration of calcium ions is -1622 kJ/mol and that of chloride ions is -364 kJ/mol, we can substitute these values into the equation:H =  1  -1622 kJ/mol  +  2  -364 kJ/mol H = -1622 kJ/mol - 728 kJ/molH = -2350 kJ/molThis is the enthalpy change of hydration for 1 mole of calcium chloride. Now, we need to calculate the heat of crystallization for 5 moles of calcium chloride:Heat of crystallization = 5 moles  HHeat of crystallization = 5  -2350 kJ/molHeat of crystallization = -11750 kJSo, the heat of crystallization of 5 moles of calcium chloride is -11750 kJ.