A. Use the following data to calculate the enthalpy of hydration for calcium chloride and calcium iodide.
Lattice Energy* ΔHsoln
CaCl_2(s) -2247 kJ/mol -46 kJ/mol
CaI_2(s) -2059 kJ/mol -104 kJ/mol
*Lattice energy is defined as the energy change for the process M^+(g) + X^-(g) > MX(s).
b. Based on your answers to part a, which ion, Cl^- or I^-, is more strongly attracted to water?
O Chloride
O Iodide

A. Enthalpy of hydration of CaCl2 = -2293 KJ/mol

Enthalpy of hydration of CaI2 = -2163 KJ/mol

B. Chloride ions

Explanation:

Enthalpy of hydration is the energy required to convert one mole of gaseous ions to aqueousions.

Enthalpy of hydration = Enthalpy of solution - lattice energy

For CaCl2;

Enthalpy of hydration = -46 - 2247 = -2293 KJ/mol

For CaI2;

Enthalpy of hydration = -104 - 2059 = -2163 KJ/mol

B. Since the enthalpy of hydration of CaCl2 is more negative than that of CaI2, it means that chloride ions are more easily attracted to water molecules. This we conclude because the difference in enthalpy values are due to the negative ions as the two compounds share a common positive calcium ion.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.